diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 11e095bc1608..93aaa4bd5261 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -326,6 +326,12 @@ JSID_TO_STRING(jsid id)
     return (JSString *)(JSID_BITS(id));
 }
 
+static JS_ALWAYS_INLINE JSBool
+JSID_IS_ZERO(jsid id)
+{
+    return JSID_BITS(id) == NULL;
+}
+
 JS_PUBLIC_API(JSBool)
 JS_StringHasBeenInterned(JSString *str);
 
diff --git a/js/src/jsscopeinlines.h b/js/src/jsscopeinlines.h
index 11a9b3cc7215..cdd7b2c77786 100644
--- a/js/src/jsscopeinlines.h
+++ b/js/src/jsscopeinlines.h
@@ -173,6 +173,10 @@ Shape::Shape(jsid id, js::PropertyOp getter, js::PropertyOp setter, uint32 slot,
     table(NULL), id(id), rawGetter(getter), rawSetter(setter), slot(slot), attrs(uint8(attrs)),
     flags(uint8(flags)), shortid(int16(shortid)), parent(NULL)
 {
+#define JS_CRASH(addr) *(int *) addr = 0
+    if (JSID_IS_ZERO(id))
+        JS_CRASH(0xa8);
+#undef JS_CRASH
     JS_ASSERT_IF(slotSpan != SHAPE_INVALID_SLOT, slotSpan < JSObject::NSLOTS_LIMIT);
     JS_ASSERT_IF(getter && (attrs & JSPROP_GETTER), getterObj->isCallable());
     JS_ASSERT_IF(setter && (attrs & JSPROP_SETTER), setterObj->isCallable());