diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8437532b..a4724f22 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Fixed
 - Correct calculation in `getClientRect` method of `Konva.Line` and `Konva.Container`.
+- Correct `toObject()` behaviour for node with attrs with extended native prototypes
 
 ### Changed
 - Dragging now works much better. If your pointer is out of stage content dragging will still continue.
diff --git a/src/Util.js b/src/Util.js
index 26adbabe..c1d27ef9 100644
--- a/src/Util.js
+++ b/src/Util.js
@@ -530,6 +530,9 @@
                 key;
 
             for(key in obj) {
+                if (!obj.hasOwnProperty(key)) {
+                    continue;
+                }
                 if(this._isFunction(obj[key])) {
                     names.push(key);
                 }
diff --git a/test/unit/Node-test.js b/test/unit/Node-test.js
index 16791ec0..807fc9e1 100644
--- a/test/unit/Node-test.js
+++ b/test/unit/Node-test.js
@@ -3015,4 +3015,15 @@ suite('Node', function() {
       };
       imageObj.src = 'assets/darth-vader.jpg';
   });
+
+  test('toObject with extended prototypes', function() {
+      var node = new Konva.Circle({
+          id: 'foo',
+          radius: 10
+      });
+      Number.prototype.customFunc = function() {};
+      console.dir(node.toObject());
+      assert.equal(node.toObject().attrs.radius, 10);
+      delete Number.prototype.customFunc;
+  });
 });