diff --git a/test/unit/base.html b/test/unit/base.html
index cb67fd8ff3..b55a768dca 100644
--- a/test/unit/base.html
+++ b/test/unit/base.html
@@ -42,6 +42,10 @@
     }
   };
   instance = Object.create(Child);
+  // make __proto__ work on IE10.
+  if (!Object.__proto__) {
+    instance.__proto__ = Child;
+  }
 });
 
 suite('addFeature', function() {