error handling in 'wrap' does not coerce numbers into string messages

lcorolib.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lcorolib.c,v 1.8 2014/10/25 11:50:46 roberto Exp roberto $
+** $Id: lcorolib.c,v 1.9 2014/11/02 19:19:04 roberto Exp roberto $
 ** Coroutine Library
 ** See Copyright Notice in lua.h
 */
@@ -75,7 +75,7 @@ static int luaB_auxwrap (lua_State *L) {
   lua_State *co = lua_tothread(L, lua_upvalueindex(1));
   int r = auxresume(L, co, lua_gettop(L));
   if (r < 0) {
-    if (lua_isstring(L, -1)) {  /* error object is a string? */
+    if (lua_type(L, -1) == LUA_TSTRING) {  /* error object is a string? */
       luaL_where(L, 1);  /* add extra info */
       lua_insert(L, -2);
       lua_concat(L, 2);