Index: parser/Parser.php
===================================================================
--- parser/Parser.php	(revision 104470)
+++ parser/Parser.php	(working copy)
@@ -5130,6 +5129,7 @@
 	 */
 	function disableCache() {
 		wfDebug( "Parser output marked as uncacheable.\n" );
+		if ( !$this->mOutput ) throw new MWException( "disableCache called at wrong point" );
 		$this->mOutput->setCacheTime( -1 ); // old style, for compatibility
 		$this->mOutput->updateCacheExpiry( 0 ); // new style, for consistency
 	}