diff --git a/lua/uloop.c b/lua/uloop.c
index 394970d..ee82104 100644
--- a/lua/uloop.c
+++ b/lua/uloop.c
@@ -233,24 +233,23 @@ static int ul_ufd_add(lua_State *L)
 	int ref;
 	int fd_ref;
 
-	flags = luaL_checkinteger(L, -1);
+	flags = luaL_checkinteger(L, 3);
 	if (!flags) {
 		lua_pushstring(L, "flags cannot be zero");
 		lua_error(L);
 	}
-	lua_pop(L, 1);
 
-	luaL_checktype(L, -1, LUA_TFUNCTION);
+	luaL_checktype(L, 2, LUA_TFUNCTION);
 
-	fd = get_sock_fd(L, -2);
+	fd = get_sock_fd(L, 1);
 
 	lua_getglobal(L, "__uloop_cb");
-	lua_pushvalue(L, -2);
+	lua_pushvalue(L, 2);
 	ref = luaL_ref(L, -2);
 	lua_pop(L, 1);
 
 	lua_getglobal(L, "__uloop_fds");
-	lua_pushvalue(L, -3);
+	lua_pushvalue(L, 1);
 	fd_ref = luaL_ref(L, -2);
 	lua_pop(L, 1);