diff --git a/packages/zone.js/lib/common/to-string.ts b/packages/zone.js/lib/common/to-string.ts
index 3ae8d0e99d..7722623c7a 100644
--- a/packages/zone.js/lib/common/to-string.ts
+++ b/packages/zone.js/lib/common/to-string.ts
@@ -49,9 +49,10 @@ Zone.__load_patch('toString', (global: any) => {
   const originalObjectToString = Object.prototype.toString;
   const PROMISE_OBJECT_TO_STRING = '[object Promise]';
   Object.prototype.toString = function() {
-    if (this instanceof Promise) {
+    if (typeof Promise === 'function' && this instanceof Promise) {
       return PROMISE_OBJECT_TO_STRING;
     }
+
     return originalObjectToString.call(this);
   };
 });
diff --git a/packages/zone.js/test/common/toString.spec.ts b/packages/zone.js/test/common/toString.spec.ts
index d959df23f1..d1f0320726 100644
--- a/packages/zone.js/test/common/toString.spec.ts
+++ b/packages/zone.js/test/common/toString.spec.ts
@@ -18,6 +18,18 @@ describe('global function patch', () => {
           .toEqual(Function.prototype.toString.call(g[zoneSymbol('setTimeout')]));
     });
 
+    it('should not throw error if Promise is not a function', () => {
+      const P = g.Promise;
+      try {
+        g.Promise = undefined;
+        expect(() => {
+          const a = {}.toString();
+        }).not.toThrow();
+      } finally {
+        g.Promise = P;
+      }
+    });
+
     it('MutationObserver toString should be the same with native version',
        ifEnvSupports('MutationObserver', () => {
          const nativeMutationObserver = g[zoneSymbol('MutationObserver')];