diff --git a/js/src/jsfriendapi.h b/js/src/jsfriendapi.h
index 446be8bf7034..abc5fc497495 100644
--- a/js/src/jsfriendapi.h
+++ b/js/src/jsfriendapi.h
@@ -1492,7 +1492,7 @@ JSID_TO_ATOM(jsid id)
     return (JSAtom *)JSID_TO_STRING(id);
 }
 
-JS_STATIC_ASSERT(sizeof(jsid) == JS_BYTES_PER_WORD);
+JS_STATIC_ASSERT(sizeof(jsid) == sizeof(void*));
 
 namespace js {