--- weak-marking-01.js
+++ weak-marking-01.js
@@ -85,15 +85,35 @@ function deadKeys() {
 
   gc();
   assertEq(finalizeCount(), initialCount + 2);
   assertEq(nondeterministicGetWeakMapKeys(wm1).length, 0);
 }
 
 deadKeys();
 
+// The weakKeys table has to grow if it encounters enough new unmarked weakmap
+// keys. Trigger this to happen during weakmap marking.
+//
+// There's some trickiness involved in getting it to test the right thing,
+// because if a key is marked before the weakmap, then it won't get entered
+// into the weakKeys table. This chains through multiple weakmap layers to
+// ensure that the objects can't get marked before the weakmaps.
 function weakKeysRealloc() {
   var wm1 = new WeakMap;
+  var wm2 = new WeakMap;
+  var wm3 = new WeakMap;
   var obj1 = {'name': 'obj1'};
-  var wm2 = new WeakMap;
+  var obj2 = {'name': 'obj2'};
   wm1.set(obj1, wm2);
-  
+  wm2.set(obj2, wm3);
+  for (var i = 0; i < 10000; i++) {
+    wm3.set(Object.create(null), wm2);
+  }
+  wm3.set(Object.create(null), makeFinalizeObserver());
+  wm2 = undefined;
+  wm3 = undefined;
+  obj2 = undefined;
+
+  var initialCount = finalizeCount();
+  gc();
+  assertEq(finalizeCount(), initialCount + 1);
 }