diff --git a/test/utilities.js b/test/utilities.js
index 0f384fe12..512a7591c 100644
--- a/test/utilities.js
+++ b/test/utilities.js
@@ -1026,7 +1026,11 @@ describe('utilities', function () {
 
       // Ensure that foo returns an Assertion (not a function)
       expect(expect('x').x()).to.be.an.instanceOf(assertionConstructor);
-      expect(expect('x').x).to.be.an.instanceOf(assertionConstructor);
+
+      var hasProtoSupport = '__proto__' in Object;
+      if (hasProtoSupport) {
+        expect(expect('x').x).to.be.an.instanceOf(assertionConstructor);
+      }
     });
   });