diff --git a/lib/repl.js b/lib/repl.js
index 68fc116991..252d52df09 100644
--- a/lib/repl.js
+++ b/lib/repl.js
@@ -412,8 +412,8 @@ REPLServer.prototype.complete = function(line) {
             memberGroups.push(Object.getOwnPropertyNames(obj));
           }
           // works for non-objects
-          var p = obj.constructor ? obj.constructor.prototype : null;
           try {
+            var p = Object.getPrototypeOf(obj);
             var sentinel = 5;
             while (p !== null) {
               memberGroups.push(Object.getOwnPropertyNames(p));