diff --git a/es6-sham.js b/es6-sham.js
index 8e405b02..93f15b2b 100644
--- a/es6-sham.js
+++ b/es6-sham.js
@@ -151,6 +151,9 @@
       configurable: true,
       enumerable: false,
       get: function () {
+        if (this === Function.prototype) {
+          return '';
+        }
         var str = _call(functionToString, this);
         var match = _call(_strMatch, str, /\s*function\s+([^(\s]*)\s*/);
         var name = match && match[1];
diff --git a/test-sham/function.js b/test-sham/function.js
index 9b83a6a5..bbf5e8a2 100644
--- a/test-sham/function.js
+++ b/test-sham/function.js
@@ -17,6 +17,12 @@ describe('Function', function () {
       });
     });
 
+    it('does not poison every name when accessed on Function.prototype', function () {
+      expect((function foo() {}).name).to.equal('foo');
+      expect(Function.prototype.name).to.equal('');
+      expect((function foo() {}).name).to.equal('foo');
+    });
+
     it('returns empty string for anonymous functions', function () {
       var anon = identity(function () {});
       expect(anon.name).to.equal('');
diff --git a/test-sham/set-prototype-of.js b/test-sham/set-prototype-of.js
index 80448b3e..ac044a13 100644
--- a/test-sham/set-prototype-of.js
+++ b/test-sham/set-prototype-of.js
@@ -5,22 +5,22 @@ describe('Object.setPrototypeOf(o, p)', function () {
 
   it('changes prototype to regular objects', function () {
     var obj = { a: 123 };
-    expect(obj).to.be.an.instanceOf(Object);
+    expect(obj instanceof Object).to.equal(true);
     // sham requires assignment to work cross browser
     obj = Object.setPrototypeOf(obj, null);
-    expect(obj).not.to.be.an.instanceOf(Object);
+    expect(obj instanceof Object).to.equal(false);
     expect(obj.a).to.equal(123);
   });
 
   it('changes prototype to null objects', function () {
     var obj = Object.create(null);
     obj.a = 456;
-    expect(obj).not.to.be.an.instanceOf(Object);
+    expect(obj instanceof Object).to.equal(false);
     expect(obj.a).to.equal(456);
     // sham requires assignment to work cross browser
-    obj = Object.setPrototypeOf(obj, {});
-    expect(obj).to.be.an.instanceOf(Object);
+    obj = Object.setPrototypeOf(obj, { b: 789 });
+    expect(obj instanceof Object).to.equal(true);
     expect(obj.a).to.equal(456);
+    expect(obj.b).to.equal(789);
   });
-
 });