diff --git a/module/lua/lapi.c b/module/lua/lapi.c
index 726e5c2ad..ed3a0f4cf 100644
--- a/module/lua/lapi.c
+++ b/module/lua/lapi.c
@@ -250,6 +250,8 @@ LUA_API int lua_type (lua_State *L, int idx) {
 
 LUA_API const char *lua_typename (lua_State *L, int t) {
   UNUSED(L);
+  if (t > 8 || t < 0)
+    return "internal_type_error";
   return ttypename(t);
 }