diff --git a/src/Core/Sanitizer.php b/src/Core/Sanitizer.php
index 086ac1ea9..1b823d36c 100644
--- a/src/Core/Sanitizer.php
+++ b/src/Core/Sanitizer.php
@@ -965,7 +965,10 @@ class Sanitizer {
 				# * Disallow data attributes used by MediaWiki code
 				# * Ensure that the attribute is not namespaced by banning
 				#   colons.
-				if ( ( !preg_match( '/^data-[^:]*$/iD', $k ) && !isset( $list[$k] ) )
+				# * Ensure attribute name will be accepted by the HTML
+				#   parser; see
+				#   https://github.com/whatwg/dom/issues/849#issuecomment-1007541209
+				if ( ( !preg_match( '|^data-[^:= \t\r\n/>\0]*$|iD', $k ) && !isset( $list[$k] ) )
 					 || self::isReservedDataAttribute( $k )
 				) {
 					$newAttrs[$k] = [ null, $origV, $origK ];