diff --git a/src/scripting/lua_terrainmap.cpp b/src/scripting/lua_terrainmap.cpp
index 290224c68b93..e216cf9c927f 100644
--- a/src/scripting/lua_terrainmap.cpp
+++ b/src/scripting/lua_terrainmap.cpp
@@ -521,7 +521,7 @@ int intf_terrain_mask(lua_State *L)
 	if(lua_isstring(L, 3)) {
 		const std::string t_str = luaL_checkstring(L, 2);
 		std::unique_ptr<gamemap_base> mask;
-		if(auto gmap = dynamic_cast<gamemap*>(&map)) {
+		if(dynamic_cast<gamemap*>(&map)) {
 			auto mask_ptr = new gamemap("");
 			mask_ptr->read(t_str, false);
 			mask.reset(mask_ptr);