diff --git a/test/core/fixtures/transformation/es6.spec.symbols/instanceof/exec.js b/test/core/fixtures/transformation/es6.spec.symbols/instanceof/exec.js
index 983cfd7503..7d3514bf96 100644
--- a/test/core/fixtures/transformation/es6.spec.symbols/instanceof/exec.js
+++ b/test/core/fixtures/transformation/es6.spec.symbols/instanceof/exec.js
@@ -10,9 +10,11 @@ function Greeting(greeting) {
   this.greeting = greeting;
 }
 
-Greeting[Symbol.hasInstance] = function(inst) {
-  return inst.greeting == "hello";
-};
+Object.defineProperty(Greeting, Symbol.hasInstance, {
+  value: function(inst) {
+    return inst.greeting == "hello";
+  }
+});
 
 var a = new Greeting("hello");
 var b = new Greeting("world");