Index: includes/OutputPage.php
===================================================================
--- includes/OutputPage.php	(revision 21896)
+++ includes/OutputPage.php	(working copy)
@@ -364,7 +364,7 @@
 			$this->enableClientCache( false );
 		}
 		if ( $parserOutput->mHTMLtitle != "" ) {
-			$this->mPagetitle = $parserOutput->mHTMLtitle ;
+			$this->setPagetitle( $parserOutput->mHTMLtitle );
 		}
 		if ( $parserOutput->mSubtitle != '' ) {
 			$this->mSubtitle .= $parserOutput->mSubtitle ;
Index: includes/CoreParserFunctions.php
===================================================================
--- includes/CoreParserFunctions.php	(revision 21896)
+++ includes/CoreParserFunctions.php	(working copy)
@@ -98,10 +98,12 @@
 	}
 
 	static function displaytitle( $parser, $param = '' ) {
-		$parserOptions = new ParserOptions;
-		$local_parser = clone $parser;
-		$t2 = $local_parser->parse ( $param, $parser->mTitle, $parserOptions, false );
-		$parser->mOutput->mHTMLtitle = $t2->GetText();
+		$parser->mOutput->mHTMLtitle = $param;
+		$title = Title::newFromText( $param );
+		if( !is_null( $title ) && $parser->mTitle->equals( $title ) ) {
+			# No subtitle needed
+			return '';
+		}
 
 		# Add subtitle
 		$t = $parser->mTitle->getPrefixedText();