diff --git a/VisualEditor.hooks.php b/VisualEditor.hooks.php
index 1415e4bab2..1a27f4c3e2 100644
--- a/VisualEditor.hooks.php
+++ b/VisualEditor.hooks.php
@@ -79,8 +79,8 @@ class VisualEditorHooks {
 
 	public static function onDiffViewHeader(
 		DifferenceEngine $diff,
-		/* Revision */ $oldRev,
-		/* Revision */ $newRev
+		Revision $oldRev = null,
+		Revision $newRev = null
 	) {
 		$config = ConfigFactory::getDefaultInstance()->makeConfig( 'visualeditor' );
 		$output = RequestContext::getMain()->getOutput();