diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/testBug501690.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/testBug501690.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,14 @@
+function testBug501690() {
+    // Property cache assertion when 3 objects along a prototype chain have the same shape.
+    function B(){}
+    B.prototype = {x: 123};
+
+    function D(){}
+    D.prototype = new B;
+    D.prototype.x = 1;    // [1] shapeOf(B.prototype) == shapeOf(D.prototype)
+
+    arr = [new D, new D, new D, D.prototype];  // [2] all the same shape
+    for (var i = 0; i < 4; i++)
+        assertEq(arr[i].x, 1);  // same kshape [2], same vshape [1]
+}
+testBug501690();