diff --git a/src/blua/liolib.c b/src/blua/liolib.c
index a87e186e6..e6c294de0 100644
--- a/src/blua/liolib.c
+++ b/src/blua/liolib.c
@@ -249,7 +249,7 @@ static int io_open (lua_State *L) {
 	{
 		luaL_checktype(L, 3, LUA_TFUNCTION);
 	}
-	else
+	else if (lua_compatmode)
 	{
 		return io_openlocal(L);
 	}
diff --git a/src/lua_baselib.c b/src/lua_baselib.c
index 7ac322188..020a6dcf8 100644
--- a/src/lua_baselib.c
+++ b/src/lua_baselib.c
@@ -2066,12 +2066,12 @@ static int lib_pSetupLevelSky(lua_State *L)
 	NOHUD
 	INLEVEL
 
-	if (lua_isnumber(L, 1))
+	if (lua_isnumber(L, 1) && lua_compatmode)
 	{
 		skytexname = luaL_checkstring(L, 1);
 		skytexname = va("SKY%s",skytexname);
 	}
-	else if (lua_isnil(L, 1))
+	else if (lua_isnil(L, 1) && lua_compatmode)
 		skytexname = mapheaderinfo[gamemap-1]->skytexture;
 	else
 		skytexname = luaL_checkstring(L, 1);