diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/collections/Map-gc-4.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/collections/Map-gc-4.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,15 @@
+// Bug 770954.
+
+gczeal(4);
+var s = new Set;
+s.add(-0);
+s.add(0);
+assertEq(s.delete(-0), true);
+assertEq(s.has(0), (false  ));
+assertEq(s.has(-0), false);
+var m = new Map;
+m.set(-0, 'x');
+assertEq(m.has(0), true);
+assertEq(m.get(0), 'x');
+assertEq(m.has(-0), true);
+assertEq(m.delete(-0), true);