diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/ion/bug772901.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/ion/bug772901.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,7 @@
+// vim: set ts=8 sts=4 et sw=4 tw=99:
+
+function f(x) {
+    delete ((x)++);
+    arguments[0] !== undefined;
+}
+f(1, x = [f.ArrayBuffer,unwatch.Int32Array], this, this, this) ;