diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/parallel/bug977647.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/parallel/bug977647.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,12 @@
+// Check for mapPar() applied to an empty array.
+// Public domain.
+
+if (!this.hasOwnProperty("TypedObject"))
+  quit();
+
+var { ArrayType, StructType, uint32 } = TypedObject;
+var Point = new StructType({x: uint32, y: uint32});
+var Points = Point.array();
+var points = new Points();
+points.mapPar(function() {});
+