diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/parallel/binary-arith-numbers.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/parallel/binary-arith-numbers.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,30 @@
+load(libdir + "parallelarray-helpers.js");
+
+// Test that we are able to add numbers even if the typesets are not
+// "clean" because we have previously added strings and numbers.  This
+// should cause fallible unboxing to occur.
+
+function theTest() {
+  var mixedArray = [1.1, 2.2, 3.3, 4.4, 5.5, 6.6, 7.7, 8.8, 9.9, 10.1,
+                    "1", "2", "3", "4", "5", "6", "7", "8", "9", "10"];
+
+  function op(e, i) {
+    return mixedArray[e % mixedArray.length] + i;
+  }
+
+  // run op once where it has to add doubles and strings,
+  // just to pullute the typesets:
+  var jsarray0 = range(0, 1024);
+  jsarray0.map(op);
+
+  // this version will never actually touch the strings:
+  assertArraySeqParResultsEq(range(0, 1024), "map", function (i) { return i % 10; });
+
+  // but if we try against the original we get bailouts:
+  assertParallelExecWillBail(function (mode) {
+    jsarray0.mapPar(op, mode);
+  });
+}
+
+if (getBuildConfiguration().parallelJS)
+  theTest();