diff --git a/apps/twnlua/game.c b/apps/twnlua/game.c
index 6df50a5..8ce97c2 100644
--- a/apps/twnlua/game.c
+++ b/apps/twnlua/game.c
@@ -112,6 +112,12 @@ void game_tick(void) {
     State *state = ctx.udata;
 
     bindgen_build_context(state->L);
+    lua_getglobal(state->L, "ctx");
+    if (!lua_isnoneornil(state->L, -1)) {
+        lua_getfield(state->L, -1, "udata");
+        lua_setfield(state->L, -3, "udata");
+    }
+    lua_pop(state->L, 1);
     lua_setglobal(state->L, "ctx");
 
     lua_getglobal(state->L, "game_tick");