diff --git a/wp-includes/plugin.php b/wp-includes/plugin.php
index b8148c5185..c910c851e8 100644
--- a/wp-includes/plugin.php
+++ b/wp-includes/plugin.php
@@ -737,9 +737,9 @@ function _wp_filter_build_unique_id($tag, $function, $priority) {
 	if ( is_string($function) )
 		return $function;
 
-	// Closures are currently implemented as objects
 	if ( is_object($function) ) {
-		$function = array( $function );
+		// Closures are currently implemented as objects
+		$function = array( $function, '' );
 	} else {
 		$function = (array) $function;
 	}