diff --git a/includes/revisiondelete/RevisionDeleteUser.php b/includes/revisiondelete/RevisionDeleteUser.php
index fe424efa309..0e965c82067 100644
--- a/includes/revisiondelete/RevisionDeleteUser.php
+++ b/includes/revisiondelete/RevisionDeleteUser.php
@@ -34,10 +34,10 @@ class RevisionDeleteUser {
 	 * @return bool
 	 */
 	private static function setUsernameBitfields( $name, $userId, $op, $dbw ) {
-		if( $op !== '|' && $op !== '&' ){
+		if ( !$userId || ( $op !== '|' && $op !== '&' ) ) {
 			return false; // sanity check
 		}
-		if( !$dbw instanceof DatabaseBase ){
+		if ( !$dbw instanceof DatabaseBase ) {
 			$dbw = wfGetDB( DB_MASTER );
 		}