diff --git a/lib/object.js b/lib/object.js
index <HASH>..<HASH> 100644
--- a/lib/object.js
+++ b/lib/object.js
@@ -116,6 +116,8 @@ function testOverwriteObject(callback)
 	first.overwriteWith(second);
 	testing.assertEquals(first.countProperties(), 3, 'Overwritten should have three properties', callback);
 	testing.assertEquals(first.b, 'b2', 'Property in first should be replaced with second', callback);
+	first.overwriteWith(undefined);
+	testing.assertEquals(first.countProperties(), 3, 'Overwritten with undefined should have three properties', callback);
 	testing.success(callback);
 }
 
@@ -127,10 +129,10 @@ core.addProperties(Object.prototype, newObject);
  */
 exports.test = function(callback)
 {
-	var tests = {
-		testCountProperties: testCountProperties,
-		overwrite: testOverwriteObject,
-	};
+	var tests = [
+		testCountProperties,
+		testOverwriteObject,
+	];
 	testing.run(tests, callback);
 };
Test that overwriting with undefined does not crash.