diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/testBug878429.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/testBug878429.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,9 @@
+function negZeroMinusNegZero()
+{
+  var x = -0.0;
+  var y = -0.0;
+  return +(x - y);
+}
+
+assertEq(1 / negZeroMinusNegZero(), Infinity);
+assertEq(1 / negZeroMinusNegZero(), Infinity);