diff --git a/lodash.js b/lodash.js
index 8e216fc1e..8ff413c50 100644
--- a/lodash.js
+++ b/lodash.js
@@ -6572,8 +6572,11 @@
      * // => ['x', 'y'] (property order is not guaranteed across environments)
      */
     var keys = !nativeKeys ? shimKeys : function(object) {
-      var length = object ? object.length : 0;
-      if (typeof length == 'number' && length > 0) {
+      var ctor = object && object.constructor,
+          length = object ? object.length : 0;
+
+      if (typeof length == 'number' && length > 0 ||
+          (ctor && object === ctor.prototype)) {
         return shimKeys(object);
       }
       return isObject(object) ? nativeKeys(object) : [];
@@ -6609,7 +6612,9 @@
           (support.nonEnumArgs && isArguments(object))) && length) >>> 0;
 
       var keyIndex,
+          ctor = object.constructor,
           index = -1,
+          isProto = ctor && object === ctor.prototype,
           maxIndex = length - 1,
           result = Array(length),
           skipIndexes = length > 0,
@@ -6620,7 +6625,8 @@
         result[index] = String(index);
       }
       for (var key in object) {
-        if (!(skipProto && key == 'prototype') &&
+        if (!(isProto && key == 'constructor') &&
+            !(skipProto && key == 'prototype') &&
             !(skipErrorProps && (key == 'message' || key == 'name')) &&
             !(skipIndexes && (keyIndex = +key, keyIndex > -1 && keyIndex <= maxIndex && keyIndex % 1 == 0))) {
           result.push(key);
@@ -6631,11 +6637,10 @@
       // attribute of an existing property and the `constructor` property of a
       // prototype defaults to non-enumerable.
       if (support.nonEnumShadows && object !== objectProto) {
-        var ctor = object.constructor;
         index = -1;
         length = shadowedProps.length;
 
-        if (object === (ctor && ctor.prototype)) {
+        if (isProto) {
           var className = object === stringProto ? stringClass : object === errorProto ? errorClass : toString.call(object),
               nonEnum = nonEnumProps[className];
         }
diff --git a/test/test.js b/test/test.js
index 58d7cce1f..ba96e7113 100644
--- a/test/test.js
+++ b/test/test.js
@@ -5493,23 +5493,16 @@
       delete String.prototype.a;
     });
 
-    test('`_.' + methodName + '` fixes the JScript `[[DontEnum]]` bug (test in IE < 9)', 2, function() {
-      function Foo() {}
-      Foo.prototype.a = 1;
-
-      var actual = func(Foo.prototype);
-      deepEqual(actual, ['a']);
-
-      actual = func(shadowedObject);
+    test('`_.' + methodName + '` fixes the JScript `[[DontEnum]]` bug (test in IE < 9)', 1, function() {
+      var actual = func(shadowedObject);
       deepEqual(actual.sort(), shadowedProps);
     });
 
     test('`_.' + methodName + '` skips the prototype property of functions (test in Firefox < 3.6, Opera > 9.50 - Opera < 11.60, and Safari < 5.1)', 2, function() {
       function Foo() {}
-      Foo.prototype.c = 3;
-
       Foo.a = 1;
       Foo.b = 2;
+      Foo.prototype.c = 3;
 
       var expected = ['a', 'b'],
           actual = func(Foo);
@@ -5518,10 +5511,20 @@
 
       Foo.prototype = { 'c': 3 };
       actual = func(Foo);
-
       deepEqual(actual.sort(), expected);
     });
 
+    test('`_.' + methodName + '` skips the `constructor` property on prototype objects', 2, function() {
+      function Foo() {}
+      Foo.prototype.a = 1;
+
+      var expected = ['a'];
+      deepEqual(func(Foo.prototype), ['a']);
+
+      Foo.prototype = { 'constructor': Foo, 'a': 1 };
+      deepEqual(func(Foo.prototype), ['a']);
+    });
+
     test('`_.' + methodName + '` should ' + (isKeys ? 'not' : '') + ' include inherited properties', 1, function() {
       function Foo() {
         this.a = 1;