diff --git a/src/utils.js b/src/utils.js
index d93f10c50c2e..7a4d59e0803f 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -39,7 +39,11 @@ function isString(what) {
 }
 
 function isEmptyObject(what) {
-  for (var _ in what) return false; // eslint-disable-line guard-for-in, no-unused-vars
+  for (var _ in what) {
+    if (what.hasOwnProperty(_)) {
+      return false;
+    }
+  }
   return true;
 }
 
diff --git a/test/utils.test.js b/test/utils.test.js
index 7da12461bfd7..8f2b66c641f8 100644
--- a/test/utils.test.js
+++ b/test/utils.test.js
@@ -64,6 +64,12 @@ describe('utils', function() {
     it('should work as advertised', function() {
       assert.isTrue(isEmptyObject({}));
       assert.isFalse(isEmptyObject({foo: 1}));
+      var MyObj = function() {};
+      MyObj.prototype.foo = 0;
+      assert.isTrue(isEmptyObject(new MyObj()));
+      var myExample = new MyObj();
+      myExample.bar = 1;
+      assert.isFalse(isEmptyObject(myExample));
     });
   });