diff --git a/lualib-src/lua-cluster.c b/lualib-src/lua-cluster.c
index 47c6592d..a050f3c0 100644
--- a/lualib-src/lua-cluster.c
+++ b/lualib-src/lua-cluster.c
@@ -111,7 +111,11 @@ packreq_string(lua_State *L, int session, void * msg, uint32_t sz, int is_push)
 	const char *name = lua_tolstring(L, 1, &namelen);
 	if (name == NULL || namelen < 1 || namelen > 255) {
 		skynet_free(msg);
-		luaL_error(L, "name is too long %s", name);
+		if (name == NULL) {
+			luaL_error(L, "name is not a string, it's a %s", lua_typename(L, lua_type(L, 1)));
+		} else {
+			luaL_error(L, "name is too long %s", name);
+		}
 	}
 
 	uint8_t buf[TEMP_LENGTH];