diff --git a/lib/simpletestlib.php b/lib/simpletestlib.php
index 400b22ad99d..72d75f35559 100644
--- a/lib/simpletestlib.php
+++ b/lib/simpletestlib.php
@@ -199,7 +199,8 @@ abstract class XMLStructureExpectation extends SimpleExpectation {
     	if (!$parser->loadXML('<html>' . $html . '</html>')) {
     		$parser = new DOMDocument();
     	}
-        libxml_use_internal_errors($prevsetting);
+        libxml_clear_errors();
+    	libxml_use_internal_errors($prevsetting);
     	return $parser;
     }
 }