diff --git a/src/promise.js b/src/promise.js
index 10dc52a40..862cc52ad 100644
--- a/src/promise.js
+++ b/src/promise.js
@@ -754,6 +754,14 @@ Promise.prototype._settledValue = function() {
     // Implicit undefined for cancelled promise.
 };
 
+if (typeof Symbol !== "undefined" && Symbol.toStringTag) {
+    es5.defineProperty(Promise.prototype, Symbol.toStringTag, {
+        get: function () {
+            return "Object";
+        }
+    });
+}
+
 function deferResolve(v) {this.promise._resolveCallback(v);}
 function deferReject(v) {this.promise._rejectCallback(v, false);}