diff --git a/src/ZestInst.php b/src/ZestInst.php
index b05f2fb..82ba8de 100644
--- a/src/ZestInst.php
+++ b/src/ZestInst.php
@@ -1,1189 +1,1216 @@
 <?php
 
 namespace Wikimedia\Zest;
 
 use \DOMDocument as DOMDocument;
 use \DOMElement as DOMElement;
 use \DOMNode as DOMNode;
 use \DOMNodeList as DOMNodeList;
 
 use \Error as Error;
 use \InvalidArgumentException as InvalidArgumentException;
 
 /**
  * Zest.php (https://github.com/wikimedia/zest.php)
  * Copyright (c) 2019, C. Scott Ananian. (MIT licensed)
  * PHP port based on:
  *
  * Zest (https://github.com/chjj/zest)
  * A css selector engine.
  * Copyright (c) 2011-2012, Christopher Jeffrey. (MIT Licensed)
  * Domino version based on Zest v0.1.3 with bugfixes applied.
  */
 
 class ZestInst {
 
 	/**
 	 * Helpers
 	 */
 
 	/*
 $compareDocumentPosition = function ( $a, $b ) {
 	return $a->compareDocumentPosition( $b );
 };
 
 $order = function ( $a, $b ) use ( &$compareDocumentPosition ) {
 	return ( $compareDocumentPosition( $a, $b ) & 2 ) ? 1 : -1;
 };
 	*/
 
 	private static function next( DOMNode $el ): ?DOMNode {
 		while ( ( $el = $el->nextSibling ) && $el->nodeType !== 1 ) {
 			// no op
 		}
 		return $el;
 	}
 
 	private static function prev( DOMNode $el ): ?DOMNode {
 		while ( ( $el = $el->previousSibling ) && $el->nodeType !== 1 ) {
 			// no op
 		}
 		return $el;
 	}
 
 	private static function child( DOMNode $el ): ?DOMNode {
 		if ( $el = $el->firstChild ) {
 			while ( $el->nodeType !== 1 && ( $el = $el->nextSibling ) ) {
 				// no op
 			}
 		}
 		return $el;
 	}
 
 	private static function lastChild( DOMNode $el ): ?DOMNode {
 		if ( $el = $el->lastChild ) {
 			while ( $el->nodeType !== 1 && ( $el = $el->previousSibling ) ) {
 				// no op
 			}
 		}
 		return $el;
 	}
 
 	private static function parentIsElement( DOMNode $n ): bool {
 		if ( !$n->parentNode ) { return false;
   }
 		$nodeType = $n->parentNode->nodeType;
 		// The root `html` element can be a first- or last-child, too.
 		return $nodeType === 1 || $nodeType === 9;
 	}
 
 	private static function unichr( int $codepoint ): string {
 		if ( extension_loaded( 'intl' ) ) {
 			// @phan-suppress-next-line PhanUndeclaredClassMethod
 			return \IntlChar::chr( $codepoint );
 		} else {
 			return mb_chr( $codepoint, "utf-8" );
 		}
 	}
 
 	private static function unquote( string $str ): string {
 		if ( !$str ) {
 			return $str;
 		}
 		self::initRules();
 		$ch = $str[ 0 ];
 		if ( $ch === '"' || $ch === "'" ) {
 			if ( substr( $str, - 1 ) === $ch ) {
 				$str = substr( $str, 1, -1 );
 			} else {
 				// bad string.
 				$str = substr( $str, 1 );
 			}
 			return preg_replace_callback( self::$rules->str_escape, function ( array $matches ) {
 				$s = $matches[0];
 				if ( !preg_match( '/^\\\(?:([0-9A-Fa-f]+)|([\r\n\f]+))/', $s, $m ) ) {
 					return substr( $s, 1 );
 				}
 				if ( $m[ 2 ] ) {
 					return ''; /* escaped newlines are ignored in strings. */
 				}
 				$cp = intval( $m[ 1 ], 16 );
 				return self::unichr( $cp );
 			}, $str );
 		} elseif ( preg_match( self::$rules->ident, $str ) ) {
 			return self::decodeid( $str );
 		} else {
 			// NUMBER, PERCENTAGE, DIMENSION, etc
 			return $str;
 		}
 	}
 
 	private static function decodeid( string $str ): string {
 		return preg_replace_callback( self::$rules->escape, function ( array $matches ) {
 			$s = $matches[0];
 			if ( !preg_match( '/^\\\([0-9A-Fa-f]+)/', $s, $m ) ) {
 				return $s[ 1 ];
 			}
 			$cp = intval( $m[ 1 ], 16 );
 			return self::unichr( $cp );
 		}, $str );
 	}
 
 	private static function makeInside( string $start, string $end ): string {
 		$regex = preg_replace(
 			'/>/', $end, preg_replace(
 				'/</', $start, self::reSource( self::$rules->inside )
 			)
 		);
 		return '/' . $regex . '/Su';
 	}
 
 	private static function reSource( string $regex ): string {
 		// strip delimiter and flags from regular expression
 		return preg_replace( '/(^\/)|(\/[a-z]*$)/Diu', '', $regex );
 	}
 
 	private static function replace( string $regex, string $name, string $val ): string {
 		$regex = self::reSource( $regex );
 		$regex = str_replace( $name, self::reSource( $val ), $regex );
 		return '/' . $regex . '/Su';
 	}
 
 	private static function truncateUrl( string $url, int $num ): string {
 		$url = preg_replace( '/^(?:\w+:\/\/|\/+)/', '', $url );
 		$url = preg_replace( '/(?:\/+|\/*#.*?)$/', '', $url );
 		return implode( '/', explode( '/', $url, $num ) );
 	}
 
 	private static function getElementsByTagName( DOMNode $context, string $tagName ): DOMNodeList {
 		// This *should* just be a call to PHP's `getElementByTagName`
 		// function *BUT* PHP's implementation is 100x slower than using
 		// XPath to get the same results (!)
 		if ( $tagName !== '*' ) {
 			// XXX this assumes default PHP DOM implementation, which
 			// reports lowercase tag names in DOMNode->tagName (even though
 			// the DOM spec says it should report uppercase)
 			$tagName = strtolower( $tagName );
 			if ( !preg_match( '/^[_a-z][-.0-9_a-z]*$/S', $tagName ) ) {
 				if ( $context instanceof DOMDocument ) {
 					// XPath doesn't have escape rules; just fall back to PHP's
 					// (extremely slow) implementation
 					return $context->getElementsByTagName( $tagName );
 				}
 				// Ugh, PHP doesn't define getElementsByTagName except on the
 				// top-level document, and XPath doesn't have escape sequences.
 				// Let's cross our fingers that the nodeName is XML-safe.
 			}
 		}
 		if ( $context instanceof DOMDocument ) {
 			$doc = $context;
 		} else {
 			$doc = $context->ownerDocument;
 		}
 		$xpath = new \DOMXPath( $doc );
 		$ns = $doc->documentElement->namespaceURI;
 		if ( $ns ) {
 			// Namespaces are important to XPath (but not in general for HTML)
 			$xpath->registerNamespace( 'ns', $ns );
 			$query = ".//ns:$tagName";
 		} else {
 			$query = ".//$tagName";
 		}
 		return $xpath->query( $query, $context );
 	}
 
 	/**
 	 * Handle `nth` Selectors
 	 */
 	private static function parseNth( string $param ): object {
 		$param = preg_replace( '/\s+/', '', $param );
 
 		if ( $param === 'even' ) {
 			$param = '2n+0';
 		} elseif ( $param === 'odd' ) {
 			$param = '2n+1';
 		} elseif ( strpos( $param, 'n' ) === false ) {
 			$param = '0n' . $param;
 		}
 
 		preg_match( '/^([+-])?(\d+)?n([+-])?(\d+)?$/', $param, $cap );
 
 		$group = intval( ( $cap[1] ?: '' ) . ( $cap[2] ?: '1' ), 10 );
 		$offset = intval( ( $cap[3] ?: '' ) . ( $cap[4] ?: '0' ), 10 );
 		return (object)[
 			'group' => $group,
 			'offset' => $offset,
 		];
 	}
 
 	private static function nth( string $param, callable $test, bool $last ): callable {
 		$param = self::parseNth( $param );
 		$group = $param->group;
 		$offset = $param->offset;
 		$find = ( !$last ) ? [ self::class, 'child' ] : [ self::class, 'lastChild' ];
 		$advance = ( !$last ) ? [ self::class, 'next' ] : [ self::class, 'prev' ];
 		return function ( DOMNode $el ) use ( $find, $test, $offset, $group, $advance ): bool {
 			if ( !self::parentIsElement( $el ) ) {
 				return false;
 			}
 
 			$rel = call_user_func( $find, $el->parentNode );
 			$pos = 0;
 
 			while ( $rel ) {
 				if ( call_user_func( $test, $rel, $el ) ) {
 					$pos++;
 				}
 				if ( $rel === $el ) {
 					$pos -= $offset;
 					return ( $group && $pos ) ?
 						( $pos % $group ) === 0 && ( $pos < 0 === $group < 0 ) :
 						!$pos;
 				}
 				$rel = call_user_func( $advance, $rel );
 			}
 			return false;
 		};
 	}
 
 	/**
 	 * Simple Selectors which take no arguments.
 	 * @var array<string,(callable(DOMNode):bool)>
 	 */
 	private $selectors0;
 
 	/**
 	 * Simple Selectors which take one argument.
 	 * @var array<string,(callable(string):(callable(DOMNode):bool))>
 	 */
 	private $selectors1;
 
 	/**
 	 * Add a custom selector that takes no parameters.
 	 * @param string $key Name of the selector
 	 * @param callable(DOMNode):bool $func
 	 *   The selector match function
 	 */
 	public function addSelector0( string $key, callable $func ) {
 		$this->selectors0[$key] = $func;
 	}
 
 	/**
 	 * Add a custom selector that takes 1 parameter, which is passed as a
 	 * string.
 	 * @param string $key Name of the selector
 	 * @param callable(string):(callable(DOMNode):bool) $func
 	 *   The selector match function
 	 */
 	public function addSelector1( string $key, callable $func ) {
 		$this->selectors1[$key] = $func;
 	}
 
 	private function initSelectors() {
 		$this->addSelector0( '*', function ( DOMNode $el ): bool {
 			return true;
 		} );
 		$this->addSelector1( 'type', function ( string $type ): callable {
 			$type = strtolower( $type );
 			return function ( DOMNode $el ) use ( $type ): bool {
 				return strtolower( $el->nodeName ) === $type;
 			};
 		} );
 		$this->addSelector0( ':first-child', function ( DOMNode $el ): bool {
 			return !self::prev( $el ) && self::parentIsElement( $el );
 		} );
 		$this->addSelector0( ':last-child', function ( DOMNode $el ): bool {
 			return !self::next( $el ) && self::parentIsElement( $el );
 		} );
 		$this->addSelector0( ':only-child', function ( DOMNode $el ): bool {
 			return !self::prev( $el ) && !self::next( $el )
 				&& self::parentIsElement( $el );
 		} );
 		$this->addSelector1( ':nth-child', function ( string $param, bool $last = false ): callable {
 			return self::nth( $param, function () {
 				return true;
 			}, $last );
 		} );
 		/** @suppress PhanParamTooMany */
 		$this->addSelector1( ':nth-last-child', function ( string $param ): callable {
 			return $this->selectors1[ ':nth-child' ]( $param, true );
 		} );
 		$this->addSelector0( ':root', function ( DOMNode $el ): bool {
 			return $el->ownerDocument->documentElement === $el;
 		} );
 		$this->addSelector0( ':empty', function ( DOMNode $el ): bool {
 			return !$el->firstChild;
 		} );
 		$this->addSelector1( ':not', function ( string $sel ) {
 			$test = self::compileGroup( $sel );
 			return function ( DOMNode $el ) use ( $test ): bool {
 				return !call_user_func( $test, $el );
 			};
 		} );
 		$this->addSelector0( ':first-of-type', function ( DOMNode $el ): bool {
 			if ( !self::parentIsElement( $el ) ) {
 				return false;
 			}
 			$type = $el->nodeName;
 			while ( $el = self::prev( $el ) ) {
 				if ( $el->nodeName === $type ) {
 					return false;
 				}
 			}
 			return true;
 		} );
 		$this->addSelector0( ':last-of-type', function ( DOMNode $el ): bool {
 			if ( !self::parentIsElement( $el ) ) {
 				return false;
 			}
 			$type = $el->nodeName;
 			while ( $el = self::next( $el ) ) {
 				if ( $el->nodeName === $type ) {
 					return false;
 				}
 			}
 			return true;
 		} );
 		$this->addSelector0( ':only-of-type', function ( DOMNode $el ): bool {
 			return $this->selectors0[ ':first-of-type' ]( $el ) &&
 				$this->selectors0[ ':last-of-type' ]( $el );
 		} );
 		$this->addSelector1( ':nth-of-type', function ( string $param, bool $last = false ): callable  {
 			return self::nth( $param, function ( DOMNode $rel, DOMNode $el ) {
 				return $rel->nodeName === $el->nodeName;
 			}, $last );
 		} );
 		/** @suppress PhanParamTooMany */
 		$this->addSelector1( ':nth-last-of-type', function ( string $param ): callable {
 			return $this->selectors1[ ':nth-of-type' ]( $param, true );
 		} );
 		$this->addSelector0( ':checked', function ( DOMNode $el ): bool {
 			'@phan-var DOMElement $el';
 			// XXX these properties don't exist in the PHP DOM
 			// return !!( $el->checked || $el->selected );
 			return (bool)( $el->hasAttribute( 'checked' ) || $el->hasAttribute( 'selected' ) );
 		} );
 		/** @suppress PhanParamTooMany, PhanTypeMismatchArgument */
 		$this->addSelector0( ':indeterminate', function ( DOMNode $el ): bool {
 			return !$this->selectors0[ ':checked' ]( $el );
 		} );
 		$this->addSelector0( ':enabled', function ( DOMNode $el ): bool {
 			'@phan-var DOMElement $el';
 			// XXX these properties don't exist in the PHP DOM
 			// return !$el->disabled && $el->type !== 'hidden';
 			return !$el->hasAttribute( 'disabled' ) && $el->getAttribute( 'type' ) !== 'hidden';
 		} );
 		$this->addSelector0( ':disabled', function ( DOMNode $el ): bool {
 			'@phan-var DOMElement $el';
 			// XXX these properties don't exist in the PHP DOM
 			// return !!$el->disabled;
 			return $el->hasAttribute( 'disabled' );
 		} );
 		/*
 		$this->addSelector0( ':target', function ( DOMNode $el ) use ( &$window ) {
 			return $el->id === $window->location->hash->substring( 1 );
 		});
 		$this->addSelector0( ':focus', function ( DOMNode $el ) {
 			return $el === $el->ownerDocument->activeElement;
 		});
 		*/
 		$this->addSelector1( ':is', function ( string $sel ): callable {
 			return self::compileGroup( $sel );
 		} );
 		// :matches is an older name for :is; see
 		// https://github.com/w3c/csswg-drafts/issues/3258
 		$this->addSelector1( ':matches', function ( string $sel ): callable {
 			return $this->selectors1[ ':is' ]( $sel );
 		} );
 		$this->addSelector1( ':nth-match', function ( string $param, bool $last = false ): callable {
 			$args = preg_split( '/\s*,\s*/', $param );
 			$arg = array_shift( $args );
 			$test = self::compileGroup( implode( ',', $args ) );
 
 			return self::nth( $arg, $test, $last );
 		} );
 		/** @suppress PhanParamTooMany */
 		$this->addSelector1( ':nth-last-match', function ( string $param ): callable {
 			return $this->selectors1[ ':nth-match' ]( $param, true );
 		} );
 		/*
 		$this->addSelector0( ':links-here', function ( DOMNode $el ) use ( &$window ) {
 			return $el . '' === $window->location . '';
 		});
 		*/
 		$this->addSelector1( ':lang', function ( string $param ): callable {
 			return function ( DOMNode $el ) use ( $param ): bool {
 				'@phan-var DOMElement $el';
 				while ( $el ) {
 					// PHP DOM doesn't have 'lang' property
 					$lang = $el->getAttribute( 'lang' );
 					if ( $lang ) {
 						return strpos( $lang, $param ) === 0;
 					}
 					$el = $el->parentNode;
 				}
 				return false;
 			};
 		} );
 		$this->addSelector1( ':dir', function ( string $param ): callable {
 			return function ( DOMNode $el ) use ( $param ): bool {
 				'@phan-var DOMElement $el';
 				while ( $el ) {
 					$dir = $el->getAttribute( 'dir' );
 					if ( $dir ) {
 						return $dir === $param;
 					}
 					$el = $el->parentNode;
 				}
 				return false;
 			};
 		} );
 		$this->addSelector0( ':scope', function ( DOMNode $el, $con = null ): bool {
 			$context = $con ?? $el->ownerDocument;
 			if ( $context->nodeType === 9 ) {
 				return $el === $context->documentElement;
 			}
 			return $el === $context;
 		} );
 		/*
 		$this->addSelector0( ':any-link', function ( DOMNode $el ):bool {
 			return gettype( $el->href ) === 'string';
 		});
 		$this->addSelector( ':local-link', function ( DOMNode $el ) use ( &$window ) {
 			if ( $el->nodeName ) {
 				return $el->href && $el->host === $window->location->host;
 			}
 			// XXX this is really selector1 not selector0
 			$param = +$el + 1;
 			return function ( DOMNode $el ) use ( &$window, $param ) {
 				if ( !$el->href ) { return;  }
 
 				$url = $window->location . '';
 				$href = $el . '';
 
 				return self::truncateUrl( $url, $param ) === self::truncateUrl( $href, $param );
 			};
 		});
 		$this->addSelector0( ':default', function ( DOMNode $el ):bool {
 			return !!$el->defaultSelected;
 		});
 		$this->addSelector0( ':valid', function ( DOMNode $el ):bool {
 			return $el->willValidate || ( $el->validity && $el->validity->valid );
 		});
 		*/
 		$this->addSelector0( ':invalid', function ( DOMNode $el ):bool {
 			return !$this->selectors0[ ':valid' ]( $el );
 		} );
 		/*
 		$this->addSelector0( ':in-range', function ( DOMNode $el ):bool {
 			return $el->value > $el->min && $el->value <= $el->max;
 		});
 		*/
 		$this->addSelector0( ':out-of-range', function ( DOMNode $el ): bool {
 			return !$this->selectors0[ ':in-range' ]( $el );
 		} );
 		$this->addSelector0( ':required', function ( DOMNode $el ): bool {
 			'@phan-var DOMElement $el';
 			return $el->hasAttribute( 'required' );
 		} );
 		$this->addSelector0( ':optional', function ( DOMNode $el ): bool {
 			return !$this->selectors0[ ':required' ]( $el );
 		} );
 		$this->addSelector0( ':read-only', function ( DOMNode $el ): bool {
 			'@phan-var DOMElement $el';
 			if ( $el->hasAttribute( 'readOnly' ) ) {
 				return true;
 			}
 
 			$attr = $el->getAttribute( 'contenteditable' );
 			$name = strtolower( $el->nodeName );
 
 			$name = $name !== 'input' && $name !== 'textarea';
 
 			return ( $name || $el->hasAttribute( 'disabled' ) ) && $attr == null;
 		} );
 		$this->addSelector0( ':read-write', function ( DOMNode $el ): bool {
 			return !$this->selectors0[ ':read-only' ]( $el );
 		} );
 		$this->addSelector0( ':hover', function ( DOMNode $el ): bool {
 			throw new Error( ':hover is not supported.' );
 		} );
 		$this->addSelector0( ':active', function ( DOMNode $el ): bool {
 			throw new Error( ':active is not supported.' );
 		} );
 		$this->addSelector0( ':link', function ( DOMNode $el ): bool {
 			throw new Error( ':link is not supported.' );
 		} );
 		$this->addSelector0( ':visited', function ( DOMNode $el ): bool {
 			throw new Error( ':visited is not supported.' );
 		} );
 		$this->addSelector0( ':column', function ( DOMNode $el ): bool {
 			throw new Error( ':column is not supported.' );
 		} );
 		$this->addSelector0( ':nth-column', function ( DOMNode $el ): bool {
 			throw new Error( ':nth-column is not supported.' );
 		} );
 		$this->addSelector0( ':nth-last-column', function ( DOMNode $el ): bool {
 			throw new Error( ':nth-last-column is not supported.' );
 		} );
 		$this->addSelector0( ':current', function ( DOMNode $el ): bool {
 			throw new Error( ':current is not supported.' );
 		} );
 		$this->addSelector0( ':past', function ( DOMNode $el ): bool {
 			throw new Error( ':past is not supported.' );
 		} );
 		$this->addSelector0( ':future', function ( DOMNode $el ): bool {
 			throw new Error( ':future is not supported.' );
 		} );
 		// Non-standard, for compatibility purposes.
 		$this->addSelector1( ':contains', function ( string $param ): callable {
 			return function ( DOMNode $el ) use ( $param ): bool {
 				$text = $el->textContent;
 				return strpos( $text, $param ) !== false;
 			};
 		} );
 		$this->addSelector1( ':has', function ( string $param ): callable {
 			return function ( DOMNode $el ) use ( $param ): bool {
 				'@phan-var DOMElement $el';
 				return count( self::find( $param, $el ) ) > 0;
 			};
 		} );
 		// Potentially add more pseudo selectors for
 		// compatibility with sizzle and most other
 		// selector engines (?).
 	}
 
 	/** @return callable(DOMNode):bool */
 	private function selectorsAttr( string $key, string $op, string $val, bool $i ): callable {
 		$op = $this->operators[ $op ];
 		return function ( DOMNode $el ) use ( $key, $i, $op, $val ): bool {
 			/* XXX: the below all assumes a more complete PHP DOM than we have
 			switch ( $key ) {
 			#case 'for':
 			#	$attr = $el->htmlFor; // Not supported in PHP DOM
 			#	break;
 			case 'class':
 				// PHP DOM doesn't support $el->className
 				// className is '' when non-existent
 				// getAttribute('class') is null
 				if ($el->hasAttributes() && $el->hasAttribute( 'class' ) ) {
 					$attr = $el->getAttribute( 'class' );
 				} else {
 					$attr = null;
 				}
 				break;
 			case 'href':
 			case 'src':
 				$attr = $el->getAttribute( $key, 2 );
 				break;
 			case 'title':
 				// getAttribute('title') can be '' when non-existent sometimes?
 				if ($el->hasAttribute('title')) {
 					$attr = $el->getAttribute( 'title' );
 				} else {
 					$attr = null;
 				}
 				break;
 				// careful with attributes with special getter functions
 			case 'id':
 			case 'lang':
 			case 'dir':
 			case 'accessKey':
 			case 'hidden':
 			case 'tabIndex':
 			case 'style':
 				if ( $el->getAttribute ) {
 					$attr = $el->getAttribute( $key );
 					break;
 				}
 				// falls through
 			default:
 				if ( $el->hasAttribute && !$el->hasAttribute( $key ) ) {
 					break;
 				}
 				$attr = ( $el[ $key ] != null ) ?
 					$el[ $key ] :
 					$el->getAttribute && $el->getAttribute( $key );
 				break;
 			}
 			*/
 			// This is our simple PHP DOM version
 			'@phan-var DOMElement $el';
 			if ( $el->hasAttributes() && $el->hasAttribute( $key ) ) {
 				$attr = $el->getAttribute( $key );
 			} else {
 				$attr = null;
 			}
 			// End simple PHP DOM version
 			if ( $attr == null ) {
 				return false;
 			}
 			$attr = $attr . '';
 			if ( $i ) {
 				$attr = strtolower( $attr );
 				$val = strtolower( $val );
 			}
 			return call_user_func( $op, $attr, $val );
 		};
 	}
 
 	/**
 	 * Attribute Operators
 	 * @var array<string,(callable(string,string):bool)>
 	 */
 	private $operators;
 
 	/**
 	 * Add a custom operator
 	 * @param string $key Name of the operator
 	 * @param callable(string,string):bool $func
 	 *   The operator match function
 	 */
 	public function addOperator( string $key, callable $func ) {
 		$this->operators[$key] = $func;
 	}
 
 	private function initOperators() {
 		$this->addOperator( '-', function ( string $attr, string $val ): bool {
 			return true;
 		} );
 		$this->addOperator( '=', function ( string $attr, string $val ): bool {
 			return $attr === $val;
 		} );
 		$this->addOperator( '*=', function ( string $attr, string $val ): bool {
 			return strpos( $attr, $val ) !== false;
 		} );
 		$this->addOperator( '~=', function ( string $attr, string $val ): bool {
 			$attrLen = strlen( $attr );
 			$valLen = strlen( $val );
 			for ( $s = 0;  $s < $attrLen;  $s = $i + 1 ) {
 				$i = strpos( $attr, $val, $s );
 				if ( $i === false ) {
 					return false;
 				}
 				$j = $i + $valLen;
 				$f = ( $i === 0 ) ? ' ' : $attr[ $i - 1 ];
 				$l = ( $j >= $attrLen ) ? ' ' : $attr[ $j ];
 				if ( $f === ' ' && $l === ' ' ) {
 					return true;
 				}
 			}
 			return false;
 		} );
 		$this->addOperator( '|=', function ( string $attr, string $val ): bool {
 			$i = strpos( $attr, $val );
 			if ( $i !== 0 ) {
 				return false;
 			}
 			$j = $i + strlen( $val );
 			if ( $j >= strlen( $attr ) ) {
 				return true;
 			}
 			$l = $attr[ $j ];
 			return $l === '-';
 		} );
 		$this->addOperator( '^=', function ( string $attr, string $val ): bool {
 			return strpos( $attr, $val ) === 0;
 		} );
 		$this->addOperator( '$=', function ( string $attr, string $val ): bool {
 			$i = strrpos( $attr, $val );
 			return $i !== false && $i + strlen( $val ) === strlen( $attr );
 		} );
 		// non-standard
 		$this->addOperator( '!=', function ( string $attr, string $val ): bool {
 			return $attr !== $val;
 		} );
 	}
 
 	/**
 	 * Combinator Logic
 	 * @var array<string,(callable(callable(DOMNode):bool):(callable(DOMNode):(?DOMNode)))>
 	 */
 	private $combinators;
 
 	/**
 	 * Add a custom combinator
 	 * @param string $key Name of the combinator
 	 * @param callable(callable(DOMNode):bool):(callable(DOMNode):(?DOMNode)) $func
 	 *   The combinator match function
 	 */
 	public function addCombinator( string $key, callable $func ) {
 		$this->combinators[$key] = $func;
 	}
 
 	private function initCombinators() {
 		$this->addCombinator( ' ', function ( callable $test ): callable {
 			return function ( DOMNode $el ) use ( $test ): ?DOMNode {
 				while ( $el = $el->parentNode ) {
 					if ( call_user_func( $test, $el ) ) {
 						return $el;
 					}
 				}
 				return null;
 			};
 		} );
 		$this->addCombinator( '>', function ( callable $test ): callable {
 			return function ( DOMNode $el ) use ( $test ): ?DOMNode {
 				if ( $el = $el->parentNode ) {
 					if ( call_user_func( $test, $el ) ) {
 						return $el;
 					}
 				}
 				return null;
 			};
 		} );
 		$this->addCombinator( '+', function ( callable $test ): callable {
 			return function ( DOMNode $el ) use ( $test ): ?DOMNode {
 				if ( $el = self::prev( $el ) ) {
 					if ( call_user_func( $test, $el ) ) {
 						return $el;
 					}
 				}
 				return null;
 			};
 		} );
 		$this->addCombinator( '~', function ( callable $test ): callable {
 			return function ( DOMNode $el ) use ( $test ): ?DOMNode {
 				while ( $el = self::prev( $el ) ) {
 					if ( call_user_func( $test, $el ) ) {
 						return $el;
 					}
 				}
 				return null;
 			};
 		} );
 		$this->addCombinator( 'noop', function ( callable $test ): callable {
 			return function ( DOMNode $el ) use ( $test ): ?DOMNode {
 				if ( call_user_func( $test, $el ) ) {
 					return $el;
 				}
 				return null;
 			};
 		} );
 	}
 
 	private static function makeRef( callable $test, string $name ): ZestFunc {
 		$node = null;
 		$ref = new ZestFunc( function ( DOMNode $el ) use ( &$node, &$ref ) : bool {
 			$doc = $el->ownerDocument;
 			$nodes = self::getElementsByTagName( $doc, '*' );
 			$i = count( $nodes );
 
 			while ( $i-- ) {
 				$node = $nodes->item( $i );
 				if ( call_user_func( $ref->test->func, $el ) ) {
 					$node = null;
 					return true;
 				}
 			}
 
 			$node = null;
 			return false;
 		} );
 
 		$ref->combinator = function ( DOMNode $el ) use ( &$node, $name, $test ): ?DOMNode {
 			if ( !$node || !( $node instanceof DOMElement ) ) {
 				return null;
 			}
 
 			$attr = $node->getAttribute( $name ) || '';
 			if ( $attr[ 0 ] === '#' ) {
 				$attr = substr( $attr, 1 );
 			}
 
 			$id = $node->getAttribute( 'id' ) || '';
 			if ( $attr === $id && call_user_func( $test, $node ) ) {
 				return $node;
 			}
 			return null;
 		};
 
 		return $ref;
 	}
 
 	/**
 	 * Grammar
 	 */
 
 	private static $rules;
 
 	public static function initRules() {
 		self::$rules = (object)[
 		'escape' => '/\\\(?:[^0-9A-Fa-f\r\n]|[0-9A-Fa-f]{1,6}[\r\n\t ]?)/',
 		'str_escape' => '/(escape)|\\\(\n|\r\n?|\f)/',
 		'nonascii' => '/[\x{00A0}-\x{FFFF}]/',
 		'cssid' => '/(?:(?!-?[0-9])(?:escape|nonascii|[-_a-zA-Z0-9])+)/',
 		'qname' => '/^ *(cssid|\*)/',
 		'simple' => '/^(?:([.#]cssid)|pseudo|attr)/',
 		'ref' => '/^ *\/(cssid)\/ */',
 		'combinator' => '/^(?: +([^ \w*.#\\\]) +|( )+|([^ \w*.#\\\]))(?! *$)/',
 		'attr' => '/^\[(cssid)(?:([^\w]?=)(inside))?\]/',
 		'pseudo' => '/^(:cssid)(?:\((inside)\))?/',
 		'inside' => "/(?:\"(?:\\\\\"|[^\"])*\"|'(?:\\\\'|[^'])*'|<[^\"'>]*>|\\\\[\"'>]|[^\"'>])*/",
 		'ident' => '/^(cssid)$/',
 		];
 		self::$rules->cssid = self::replace( self::$rules->cssid, 'nonascii', self::$rules->nonascii );
 		self::$rules->cssid = self::replace( self::$rules->cssid, 'escape', self::$rules->escape );
 		self::$rules->qname = self::replace( self::$rules->qname, 'cssid', self::$rules->cssid );
 		self::$rules->simple = self::replace( self::$rules->simple, 'cssid', self::$rules->cssid );
 		self::$rules->ref = self::replace( self::$rules->ref, 'cssid', self::$rules->cssid );
 		self::$rules->attr = self::replace( self::$rules->attr, 'cssid', self::$rules->cssid );
 		self::$rules->pseudo = self::replace( self::$rules->pseudo, 'cssid', self::$rules->cssid );
 		self::$rules->inside = self::replace( self::$rules->inside, "[^\"'>]*", self::$rules->inside );
 		self::$rules->attr = self::replace( self::$rules->attr, 'inside', self::makeInside( '\[', '\]' ) );
 		self::$rules->pseudo = self::replace( self::$rules->pseudo, 'inside', self::makeInside( '\(', '\)' ) );
 		self::$rules->simple = self::replace( self::$rules->simple, 'pseudo', self::$rules->pseudo );
 		self::$rules->simple = self::replace( self::$rules->simple, 'attr', self::$rules->attr );
 		self::$rules->ident = self::replace( self::$rules->ident, 'cssid', self::$rules->cssid );
 		self::$rules->str_escape = self::replace( self::$rules->str_escape, 'escape', self::$rules->escape );
 	}
 
 	/**
 	 * Compiling
 	 */
 
 	private function compile( string $sel ): ZestFunc {
 		$sel = preg_replace( '/^\s+|\s+$/', '', $sel );
 		$test = null;
 		$filter = [];
 		$buff = [];
 		$subject = null;
 		$qname = null;
 		$cap = null;
 		$op = null;
 		$ref = null;
 
 		while ( $sel ) {
 			if ( preg_match( self::$rules->qname, $sel, $cap ) ) {
 				$sel = substr( $sel, strlen( $cap[0] ) );
 				$qname = $cap[ 1 ];
 				$buff[] = $this->tokQname( $qname );
 			} elseif ( preg_match( self::$rules->simple, $sel, $cap, PREG_UNMATCHED_AS_NULL ) ) {
 				$sel = substr( $sel, strlen( $cap[0] ) );
 				$qname = '*';
 				$buff[] = $this->tokQname( $qname );
 				$buff[] = $this->tok( $cap );
 			} else {
 				throw new InvalidArgumentException( 'Invalid selector.' );
 			}
 
 			while ( preg_match( self::$rules->simple, $sel, $cap, PREG_UNMATCHED_AS_NULL ) ) {
 				$sel = substr( $sel, strlen( $cap[0] ) );
 				$buff[] = $this->tok( $cap );
 			}
 
 			if ( $sel && $sel[ 0 ] === '!' ) {
 				$sel = substr( $sel, 1 );
 				$subject = self::makeSubject();
 				$subject->qname = $qname;
 				$buff[] = $subject->simple;
 			}
 
 			if ( preg_match( self::$rules->ref, $sel, $cap ) ) {
 				$sel = substr( $sel, strlen( $cap[0] ) );
 				$ref = self::makeRef( self::makeSimple( $buff ), self::decodeid( $cap[ 1 ] ) );
 				$filter[] = $ref->combinator;
 				$buff = [];
 				continue;
 			}
 
 			if ( preg_match( self::$rules->combinator, $sel, $cap, PREG_UNMATCHED_AS_NULL ) ) {
 				$sel = substr( $sel, strlen( $cap[0] ) );
 				$op = $cap[ 1 ] ?? $cap[ 2 ] ?? $cap[ 3 ];
 				if ( $op === ',' ) {
 					$filter[] = $this->combinators['noop']( self::makeSimple( $buff ) );
 					break;
 				}
 			} else {
 				$op = 'noop';
 			}
 
 			if ( !isset( $this->combinators[ $op ] ) ) {
 				throw new InvalidArgumentException( 'Bad combinator: ' . $op );
 			}
 			$filter[] = $this->combinators[ $op ]( self::makeSimple( $buff ) );
 			$buff = [];
 		}
 
 		$test = self::makeTest( $filter );
 		$test->qname = $qname;
 		$test->sel = $sel;
 
 		if ( $subject ) {
 			$subject->lname = $test->qname;
 
 			$subject->test = $test;
 			$subject->qname = $subject->qname;
 			$subject->sel = $test->sel;
 			$test = $subject;
 		}
 
 		if ( $ref ) {
 			$ref->test = $test;
 			$ref->qname = $test->qname;
 			$ref->sel = $test->sel;
 			$test = $ref;
 		}
 
 		return $test;
 	}
 
 	/** @return callable(DOMNode):bool */
 	private function tokQname( string $cap ): callable {
 		// qname
 		if ( $cap === '*' ) {
 			return $this->selectors0['*'];
 		} else {
 			return $this->selectors1['type']( self::decodeid( $cap ) );
 		}
 	}
 
 	/** @return callable(DOMNode):bool */
 	private function tok( array $cap ): callable {
 		// class/id
 		if ( $cap[ 1 ] ) {
 			return $cap[ 1 ][ 0 ] === '.'
 			// XXX unescape here?  or in attr?
 				? $this->selectorsAttr( 'class', '~=', self::decodeid( substr( $cap[ 1 ], 1 ) ), false ) :
 				$this->selectorsAttr( 'id', '=', self::decodeid( substr( $cap[ 1 ], 1 ) ), false );
 		}
 
 		// pseudo-name
 		// inside-pseudo
 		if ( $cap[ 2 ] ) {
 			$id = self::decodeid( $cap[ 2 ] );
 			if ( isset( $cap[3] ) && $cap[ 3 ] ) {
 				if ( !isset( $this->selectors1[ $id ] ) ) {
 					throw new InvalidArgumentException( "Unknown Selector: $id" );
 				}
 				return $this->selectors1[ $id ]( self::unquote( $cap[ 3 ] ) );
 			} else {
 				if ( !isset( $this->selectors0[ $id ] ) ) {
 					throw new InvalidArgumentException( "Unknown Selector: $id" );
 				}
 				return $this->selectors0[ $id ];
 			}
 		}
 
 		// attr name
 		// attr op
 		// attr value
 		if ( $cap[ 4 ] ) {
 			$value = $cap[ 6 ] ?? '';
 			$i = preg_match( "/[\"'\\s]\\s*I\$/", $value );
 			if ( $i ) {
 				$value = preg_replace( '/\s*I$/i', '', $value, 1 );
 			}
 			return $this->selectorsAttr( self::decodeid( $cap[ 4 ] ), $cap[ 5 ] ?? '-', self::unquote( $value ), (bool)$i );
 		}
 
 		throw new InvalidArgumentException( 'Unknown Selector.' );
 	}
 
 	// Returns true if all $func return true
 	private static function makeSimple( array $func ): callable {
 		$l = count( $func );
 
 		// Potentially make sure
 		// `el` is truthy.
 		if ( $l < 2 ) {
 			return $func[ 0 ];
 		}
 
 		return function ( DOMNode $el ) use ( $l, $func ): bool {
 			if ( !$el ) {
 				return false;
 			}
 			for ( $i = 0;  $i < $l;  $i++ ) {
 				if ( !call_user_func( $func[ $i ], $el ) ) {
 					return false;
 				}
 			}
 			return true;
 		};
 	}
 
 	// Returns the element that all $func return
 	private static function makeTest( array $func ): ZestFunc {
 		if ( count( $func ) < 2 ) {
 			return new ZestFunc( function ( DOMNode $el ) use ( $func ): bool {
 				return (bool)call_user_func( $func[ 0 ], $el );
 			} );
 		}
 		return new ZestFunc( function ( DOMNode $el ) use ( $func ): bool {
 			$i = count( $func );
 			while ( $i-- ) {
 				if ( !( $el = call_user_func( $func[ $i ], $el ) ) ) {
 					return false;
 				}
 			}
 			return true;
 		} );
 	}
 
 	private static function makeSubject(): ZestFunc {
 		$target = null;
 
 		$subject = new ZestFunc( function ( DOMNode $el ) use ( &$subject, &$target ): bool {
 			$node = $el->ownerDocument;
 			$scope = self::getElementsByTagName( $node, $subject->lname );
 			$i = count( $scope );
 
 			while ( $i-- ) {
 				if ( call_user_func( $subject->test->func, $scope->item( $i ) ) && $target === $el ) {
 					$target = null;
 					return true;
 				}
 			}
 
 			$target = null;
 			return false;
 		} );
 
 		$subject->simple = function ( DOMNode $el ): bool {
 			$target = $el;
 			return true;
 		};
 
 		return $subject;
 	}
 
 	/**
 	 * @return callable(DOMNode):bool
 	 */
 	private function compileGroup( string $sel ): callable {
 		$test = $this->compile( $sel );
 		$tests = [ $test ];
 
 		while ( $test->sel ) {
 			$test = $this->compile( $test->sel );
 			$tests[] = $test;
 		}
 
 		if ( count( $tests ) < 2 ) {
 			return $test->func;
 		}
 
 		return function ( DOMNode $el ) use ( $tests ): bool {
 			for ( $i = 0, $l = count( $tests );  $i < $l;  $i++ ) {
 				if ( call_user_func( $tests[ $i ]->func, $el ) ) {
 					return true;
 				}
 			}
 			return false;
 		};
 	}
 
 	/**
 	 * Selection
 	 */
 
 	// $node should be a DOMDocument or a DOMElement
 	/** @param DOMDocument|DOMElement $node */
 	private function findInternal( string $sel, DOMNode $node ): array {
 		$results = [];
 		$test = $this->compile( $sel );
 		$scope = self::getElementsByTagName( $node, $test->qname );
 		$i = 0;
 		$el = null;
 
 		foreach ( $scope as $el ) {
 			if ( call_user_func( $test->func, $el ) ) {
 				$results[] = $el;
 			}
 		}
 
 		if ( $test->sel ) {
 			while ( $test->sel ) {
 				$test = $this->compile( $test->sel );
 				$scope = self::getElementsByTagName( $node, $test->qname );
 				foreach ( $scope as $el ) {
 					if ( call_user_func( $test->func, $el ) && !in_array( $el, $results ) ) {
 						$results[] = $el;
 					}
 				}
 			}
 			// $results->sort( $order );//XXX
 		}
 
 		return $results;
 	}
 
 	/**
 	 * Find elements matching a CSS selector underneath $context.
 	 * @param string $sel The CSS selector string
 	 * @param DOMDocument|DOMElement $context The scope for the search
 	 * @return array Elements matching the CSS selector
 	 */
 	public function find( string $sel, DOMNode $context ): array {
 		/* when context isn't a DocumentFragment and the selector is simple: */
 		if ( $context->nodeType !== 11 && strpos( $sel, ' ' ) === false ) {
-			if ( $sel[ 0 ] === '#' /*&& $context->rooted*/ && preg_match( '/^#[A-Z_][-A-Z0-9_]*$/', $sel ) ) {
+			// https://www.w3.org/TR/CSS21/syndata.html#value-def-identifier
+			// Valid identifiers starting with a hyphen or with escape
+			// sequences will be handled correctly by the fall-through case.
+			if ( $sel[ 0 ] === '#' /*&& $context->rooted*/ && preg_match( '/^#[A-Za-z_](?:[-A-Za-z0-9_]|[^\0-\237])*$/Su', $sel ) ) {
 				/*
 				if ( $context->doc->_hasMultipleElementsWithId ) {
 					$id = $sel->substring( 1 );
 					if ( !$context->doc->_hasMultipleElementsWithId( $id ) ) {
 						$r = $context->doc->getElementById( $id );
 						return ( $r ) ? [ $r ] : [];
 					}
 				}
 				*/
-				if ( $context instanceof \DOMDocument ) {
-					$id = substr( $sel, 1 );
-					$r = $context->getElementById( $id );
-					return ( $r ) ? [ $r ] : [];
+				// Note that the PHP implementation can't detect the case
+				// where there are multiple elements with the same ID. Alas.
+				$doc = ( $context instanceof \DOMDocument ) ?
+					$context : $context->ownerDocument;
+				$id = substr( $sel, 1 );
+				// PHP doesn't provide an DOMElement-scoped version of
+				// getElementById, so we can't call this on $context --
+				// but that's okay because (1) IDs should be unique, and
+				// (2) we verify the scope of the returned element below
+				// anyway (to work around bugs with deleted-but-not-gc'ed
+				// nodes).
+				$r = $doc->getElementById( $id );
+				// Note that we could return null here because the
+				// DOMDocument hasn't had an "id attribute" set. See:
+				// http://php.net/manual/en/domdocument.getelementbyid.php
+				if ( $r !== null ) {
+					// Verify that this node is actually rooted in the
+					// document (or in the context), since the element
+					// isn't removed from the index immediately when it
+					// is deleted.
+					for ( $parent = $r; $parent; $parent = $parent->parentNode ) {
+						if ( $parent === $context ) {
+							return [ $r ];
+						}
+					}
+					// It's possible a deleted-but-still-indexed element was
+					// shadowing a later-added element, so we can't return
+					// null here directly; fallback to a full search.
 				}
 			}
 			/*
 			if ( $sel[ 0 ] === '.' && preg_match( '/^\.\w+$/', $sel ) ) {
 				return $context->getElementsByClassName( $sel->substring( 1 ) );
 			}
 			*/
 			if ( preg_match( '/^\w+$/', $sel ) ) {
 				return iterator_to_array( self::getElementsByTagName( $context, $sel ) );
 			}
 		}
 		/* do things the hard/slow way */
 		return $this->findInternal( $sel, $context );
 	}
 
 	/**
 	 * Determine whether an element matches the given selector.
 	 * @param DOMNode $el The element to be tested
 	 * @param string $sel The CSS selector string
 	 * @return bool True iff the element matches the selector
 	 */
 	public function matches( DOMNode $el, string $sel ): bool {
 		$test = new ZestFunc( function ( DOMNode $el ):bool {
 			return true;
 		} );
 		$test->sel = $sel;
 		do {
 			$test = $this->compile( $test->sel );
 			if ( call_user_func( $test->func, $el ) ) {
 				return true;
 			}
 		} while ( $test->sel );
 		return false;
 	}
 
 	/** @var ?ZestInst */
 	private static $singleton = null;
 
 	function __construct() {
 		$z = self::$singleton;
 		$this->selectors0 = $z ? $z->selectors0 : [];
 		$this->selectors1 = $z ? $z->selectors1 : [];
 		$this->operators = $z ? $z->operators : [];
 		$this->combinators = $z ? $z->combinators : [];
 		if ( !$z ) {
 			$this->initRules();
 			$this->initSelectors();
 			$this->initOperators();
 			$this->initCombinators();
 			self::$singleton = $this;
 			// Now create another instance so that backing arrays are cloned
 			self::$singleton = new ZestInst;
 		}
 	}
 }
diff --git a/tests/ZestTest.php b/tests/ZestTest.php
index 51b7281..d550ccd 100644
--- a/tests/ZestTest.php
+++ b/tests/ZestTest.php
@@ -1,121 +1,150 @@
 <?php
 
 namespace Wikimedia\Zest\Tests;
 
 use Wikimedia\Zest\Zest;
 
 use \DOMDocument as DOMDocument;
 use \DOMNode as DOMNode;
 
 use RemexHtml\DOM;
 use RemexHtml\Tokenizer;
 use RemexHtml\TreeBuilder;
 
 class ZestTest extends \PHPUnit\Framework\TestCase {
 
 	/**
 	 * @dataProvider findProvider
 	 */
 	public function testFind( string $selector, array $expectedList ) {
 		$doc = self::loadHTML( __DIR__ . "/index.html" );
 		$matches = Zest::find( $selector, $doc );
 		$this->assertSame( count( $matches ), count( $expectedList ) );
 
 		foreach ( $matches as $m ) {
 			$path = self::toXPath( $m );
 			$this->assertContains( $path, $expectedList );
 		}
 	}
 	public function findProvider() {
 		return [
 			[ "body > header > h1", [ "/html[1]/body[1]/header[1]/h1[1]" ] ],
 			[ "h1", [ "/html[1]/body[1]/header[1]/h1[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]" ] ],
 			[ "*", [ "/html[1]", "/html[1]/head[1]", "/html[1]/head[1]/title[1]", "/html[1]/head[1]/script[1]", "/html[1]/head[1]/script[2]", "/html[1]/head[1]/script[3]", "/html[1]/head[1]/script[4]", "/html[1]/head[1]/script[5]", "/html[1]/body[1]", "/html[1]/body[1]/header[1]", "/html[1]/body[1]/header[1]/h1[1]", "/html[1]/body[1]/header[1]/h1[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[2]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[2]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[3]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[3]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[4]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[4]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]/a[1]", "/html[1]/body[1]/article[1]", "/html[1]/body[1]/article[1]/header[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]/a[1]", "/html[1]/body[1]/article[1]/header[1]/time[1]", "/html[1]/body[1]/article[1]/p[1]", "/html[1]/body[1]/article[1]/footer[1]", "/html[1]/body[1]/article[1]/footer[1]/a[1]", "/html[1]/body[1]/footer[1]", "/html[1]/body[1]/footer[1]/a[1]", "/html[1]/body[1]/footer[1]/form[1]", "/html[1]/body[1]/footer[1]/form[1]/input[1]", "/html[1]/body[1]/footer[1]/form[1]/input[2]", "/html[1]/body[1]/footer[1]/small[1]", "/html[1]/body[1]/footer[1]/small[1]/a[1]", "/html[1]/body[1]/footer[1]/a[2]" ] ],
 			[ "article > header", [ "/html[1]/body[1]/article[1]/header[1]" ] ],
 			[ "header + p", [ "/html[1]/body[1]/article[1]/p[1]" ] ],
 			[ "header ~ footer", [ "/html[1]/body[1]/article[1]/footer[1]", "/html[1]/body[1]/footer[1]" ] ],
 			[ ":root", [ "/html[1]" ] ],
 			[ ":first-child", [ "/html[1]", "/html[1]/head[1]", "/html[1]/head[1]/title[1]", "/html[1]/body[1]/header[1]", "/html[1]/body[1]/header[1]/h1[1]", "/html[1]/body[1]/header[1]/h1[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[2]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[3]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[4]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]/a[1]", "/html[1]/body[1]/article[1]/header[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]/a[1]", "/html[1]/body[1]/article[1]/footer[1]/a[1]", "/html[1]/body[1]/footer[1]/a[1]", "/html[1]/body[1]/footer[1]/form[1]/input[1]", "/html[1]/body[1]/footer[1]/small[1]/a[1]" ] ],
 			[ ":last-child", [ "/html[1]", "/html[1]/head[1]/script[5]", "/html[1]/body[1]", "/html[1]/body[1]/header[1]/h1[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[2]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[3]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[4]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]/a[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]/a[1]", "/html[1]/body[1]/article[1]/header[1]/time[1]", "/html[1]/body[1]/article[1]/footer[1]", "/html[1]/body[1]/article[1]/footer[1]/a[1]", "/html[1]/body[1]/footer[1]", "/html[1]/body[1]/footer[1]/form[1]/input[2]", "/html[1]/body[1]/footer[1]/small[1]/a[1]", "/html[1]/body[1]/footer[1]/a[2]" ] ],
 			[ "header > :first-child", [ "/html[1]/body[1]/header[1]/h1[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]" ] ],
 			[ ":empty", [ "/html[1]/head[1]/script[3]", "/html[1]/head[1]/script[4]", "/html[1]/head[1]/script[5]", "/html[1]/body[1]/footer[1]/form[1]/input[1]", "/html[1]/body[1]/footer[1]/form[1]/input[2]" ] ],
 			[ "a[rel=\"section\"]", [ "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[2]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[3]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[4]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]/a[1]" ] ],
 			[ "html header", [ "/html[1]/body[1]/header[1]", "/html[1]/body[1]/article[1]/header[1]" ] ],
 			[ ".a", [ "/html[1]/body[1]/article[1]", "/html[1]/body[1]/footer[1]/form[1]" ] ],
 			[ "#hi", [ "/html[1]/body[1]/header[1]/h1[1]" ] ],
 			[ "html > :root", [] ],
 			[ "header h1", [ "/html[1]/body[1]/header[1]/h1[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]" ] ],
 			[ "article p", [ "/html[1]/body[1]/article[1]/p[1]" ] ],
 			[ ":not(a)", [ "/html[1]", "/html[1]/head[1]", "/html[1]/head[1]/title[1]", "/html[1]/head[1]/script[1]", "/html[1]/head[1]/script[2]", "/html[1]/head[1]/script[3]", "/html[1]/head[1]/script[4]", "/html[1]/head[1]/script[5]", "/html[1]/body[1]", "/html[1]/body[1]/header[1]", "/html[1]/body[1]/header[1]/h1[1]", "/html[1]/body[1]/header[1]/nav[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[2]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[3]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[4]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]", "/html[1]/body[1]/article[1]", "/html[1]/body[1]/article[1]/header[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]", "/html[1]/body[1]/article[1]/header[1]/time[1]", "/html[1]/body[1]/article[1]/p[1]", "/html[1]/body[1]/article[1]/footer[1]", "/html[1]/body[1]/footer[1]", "/html[1]/body[1]/footer[1]/form[1]", "/html[1]/body[1]/footer[1]/form[1]/input[1]", "/html[1]/body[1]/footer[1]/form[1]/input[2]", "/html[1]/body[1]/footer[1]/small[1]" ] ],
 			[ ".bar", [ "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[2]/a[1]" ] ],
 			[ "[id=\"hi\"]", [ "/html[1]/body[1]/header[1]/h1[1]" ] ],
 			[ "h1 + time[datetime]", [ "/html[1]/body[1]/article[1]/header[1]/time[1]" ] ],
 			[ "h1 + time[datetime]:last-child", [ "/html[1]/body[1]/article[1]/header[1]/time[1]" ] ],
 			[ ":nth-child(2n+1)", [ "/html[1]", "/html[1]/head[1]", "/html[1]/head[1]/title[1]", "/html[1]/head[1]/script[2]", "/html[1]/head[1]/script[4]", "/html[1]/body[1]/header[1]", "/html[1]/body[1]/header[1]/h1[1]", "/html[1]/body[1]/header[1]/h1[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[2]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[3]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[3]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[4]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]/a[1]", "/html[1]/body[1]/article[1]/header[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]/a[1]", "/html[1]/body[1]/article[1]/footer[1]", "/html[1]/body[1]/article[1]/footer[1]/a[1]", "/html[1]/body[1]/footer[1]", "/html[1]/body[1]/footer[1]/a[1]", "/html[1]/body[1]/footer[1]/form[1]/input[1]", "/html[1]/body[1]/footer[1]/small[1]", "/html[1]/body[1]/footer[1]/small[1]/a[1]" ] ],
 			[ ":nth-child(2n-1)", [ "/html[1]", "/html[1]/head[1]", "/html[1]/head[1]/title[1]", "/html[1]/head[1]/script[2]", "/html[1]/head[1]/script[4]", "/html[1]/body[1]/header[1]", "/html[1]/body[1]/header[1]/h1[1]", "/html[1]/body[1]/header[1]/h1[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[2]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[3]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[3]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[4]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]/a[1]", "/html[1]/body[1]/article[1]/header[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]/a[1]", "/html[1]/body[1]/article[1]/footer[1]", "/html[1]/body[1]/article[1]/footer[1]/a[1]", "/html[1]/body[1]/footer[1]", "/html[1]/body[1]/footer[1]/a[1]", "/html[1]/body[1]/footer[1]/form[1]/input[1]", "/html[1]/body[1]/footer[1]/small[1]", "/html[1]/body[1]/footer[1]/small[1]/a[1]" ] ],
 			[ ":nth-of-type(2n+1)", [ "/html[1]", "/html[1]/head[1]", "/html[1]/head[1]/title[1]", "/html[1]/head[1]/script[1]", "/html[1]/head[1]/script[3]", "/html[1]/head[1]/script[5]", "/html[1]/body[1]", "/html[1]/body[1]/header[1]", "/html[1]/body[1]/header[1]/h1[1]", "/html[1]/body[1]/header[1]/h1[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[2]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[3]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[3]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[4]/a[1]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]", "/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[5]/a[1]", "/html[1]/body[1]/article[1]", "/html[1]/body[1]/article[1]/header[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]", "/html[1]/body[1]/article[1]/header[1]/h1[1]/a[1]", "/html[1]/body[1]/article[1]/header[1]/time[1]", "/html[1]/body[1]/article[1]/p[1]", "/html[1]/body[1]/article[1]/footer[1]", "/html[1]/body[1]/article[1]/footer[1]/a[1]", "/html[1]/body[1]/footer[1]", "/html[1]/body[1]/footer[1]/a[1]", "/html[1]/body[1]/footer[1]/form[1]", "/html[1]/body[1]/footer[1]/form[1]/input[1]", "/html[1]/body[1]/footer[1]/small[1]", "/html[1]/body[1]/footer[1]/small[1]/a[1]" ] ],
 			// Child selectors on the document element `html`
 			[ "html:first-child", [ '/html[1]' ] ],
 			[ "html:only-child", [ '/html[1]' ] ],
 			[ "html:last-child", [ '/html[1]' ] ],
 			[ "html:first-of-type", [ '/html[1]' ] ],
 			[ "html:last-of-type", [ '/html[1]' ] ],
 			[ "html:nth-child(1)", [ '/html[1]' ] ],
 			[ "html:nth-child(2)", [] ],
 			[ "html:nth-last-child(1)", [ '/html[1]' ] ],
 			[ "html:nth-last-child(2)", [] ],
 			[ "html:nth-of-type(1)", [ '/html[1]' ] ],
 			[ "html:nth-of-type(2)", [] ],
 			[ "html:nth-last-of-type(1)", [ '/html[1]' ] ],
 			[ "html:nth-last-of-type(2)", [] ],
 			// The :contains selector
 			[ 'header:contains("A Date")', [ '/html[1]/body[1]/article[1]/header[1]' ] ],
 			// The :has selector
 			[ 'li:has(a[rel=section].foo)', [ '/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[1]', '/html[1]/body[1]/header[1]/nav[1]/ul[1]/li[2]' ] ],
 			// CSS escapes
 			[ "#cite_note-13\\.3F_It_Can\\'t_Be\\!-3", [ '/html[1]/body[1]/footer[1]/a[2]' ] ],
 			[ '#\\a9', [ '/html[1]/body[1]/footer[1]/small[1]/a[1]' ] ],
 		];
 	}
 
+	/**
+	 * @dataProvider findIdProvider
+	 */
+	public function testFindId( bool $useRemex ) {
+		if ( $useRemex ) {
+			$doc = self::loadHTML( __DIR__ . "/index.html" );
+		} else {
+			$doc = new DOMDocument;
+			$doc->loadHTMLFile( __DIR__ . "/index.html", LIBXML_NOERROR );
+		}
+		$matches = Zest::find( '#hi', $doc );
+		$this->assertSame( count( $matches ), 1 );
+		$el0 = $matches[0];
+		$ns = $doc->documentElement->namespaceURI;
+		$el1 = $doc->createElementNS( $ns, 'p' );
+		$el1->setAttribute( 'id', 'hi' );
+		$el2 = $doc->createElementNS( $ns, 'a' );
+		$el2->setAttribute( 'id', 'hi' );
+		Zest::find( 'body', $doc )[0]->appendChild( $el2 );
+		$el0->parentNode->removeChild( $el0 );
+		$matches = Zest::find( '#hi', $doc );
+		$this->assertSame( count( $matches ), 1 );
+		$this->assertContains( $el2, $matches );
+	}
+
+	public function findIdProvider() {
+		return [ [ false ], [ true ] ];
+	}
+
 	public static function toXPath( DOMNode $node ) {
 		// which child of parent is this?
 		$parent = $node->parentNode;
 		if ( !$parent ) {
 			return '';
 		}
 		$name = $node->nodeName;
 		if ( $name === 'html' ) {
 			return '/html[1]';
 		}
 		$count = 0;
 		foreach ( $parent->childNodes as $n ) {
 			if ( $n->nodeName === $name ) {
 				$count++;
 			}
 			if ( $n === $node ) {
 				break;
 			}
 		}
 		return self::toXPath( $parent ) . "/" . $name . "[$count]";
 	}
 	public static function loadHtml( string $filename ) : DOMDocument {
 		$text = file_get_contents( $filename );
 		return self::parseHtml( $text );
 	}
 
 	public static function parseHtml( string $text ) : DOMDocument {
 		$domBuilder = new DOM\DOMBuilder;
 		$treeBuilder = new TreeBuilder\TreeBuilder( $domBuilder, [
 			/* tree builder options */
 		] );
 		$dispatcher = new TreeBuilder\Dispatcher( $treeBuilder );
 		$tokenizer = new Tokenizer\Tokenizer( $dispatcher, $text, [
 			/* tokenizer options */
 		] );
 		$tokenizer->execute( [
 			/* execute options */
 		] );
 		return $domBuilder->getFragment();
 	}
 }