diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/testInitelemCond.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/testInitelemCond.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,13 @@
+
+/* Element initializers with unknown index. */
+
+function foo(i) {
+  var x = [1,2,i == 1 ? 3 : 4,5,6];
+  var y = "" + x;
+  if (i == 1)
+    assertEq(y, "1,2,3,5,6");
+  else
+    assertEq(y, "1,2,4,5,6");
+}
+for (var i = 0; i < 10; i++)
+  foo(i);