diff --git a/js/src/vm/Stack.cpp b/js/src/vm/Stack.cpp
index 7ae495f48c3..79214979296 100644
--- a/js/src/vm/Stack.cpp
+++ b/js/src/vm/Stack.cpp
@@ -758,7 +758,7 @@ ContextStack::pushDummyFrame(JSContext *cx, JSCompartment *dest, JSObject &scope
     uintN nvars = VALUES_PER_STACK_FRAME;
     Value *firstUnused = ensureOnTop(cx, REPORT_ERROR, nvars, CAN_EXTEND, &dfg->pushedSeg_, dest);
     if (!firstUnused)
-        return NULL;
+        return false;
 
     StackFrame *fp = reinterpret_cast<StackFrame *>(firstUnused);
     fp->initDummyFrame(cx, scopeChain);