diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/parallel/bug944975.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/parallel/bug944975.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,17 @@
+if (getBuildConfiguration().parallelJS) {
+  var map_toSource_called = false;
+  var mapPar_toSource_called = false;
+
+  Array.prototype.mapPar.toSource = function() {
+    mapPar_toSource_called = true;
+  };
+
+  Array.prototype.map.toSource = function() {
+    map_toSource_called = true;
+  };
+
+  try { new Array.prototype.mapPar; } catch (e) {}
+  try { new Array.prototype.map; } catch (e) {}
+
+  assertEq(map_toSource_called, mapPar_toSource_called);
+}