diff --git a/src/savegame_json.cpp b/src/savegame_json.cpp
index 72cddd63c5cbd..e34ccd009d7f1 100644
--- a/src/savegame_json.cpp
+++ b/src/savegame_json.cpp
@@ -4583,12 +4583,12 @@ void ter_furn_migrations::load( const JsonObject &jo )
         ter_str_id from_ter;
         mandatory( jo, false, "from_ter", from_ter );
         mandatory( jo, false, "to_ter", to_ter );
-        optional( jo, false, "to_furn", to_furn );
+        optional( jo, false, "to_furn", to_furn, furn_str_id::NULL_ID() );
         ter_migrations.insert( std::make_pair( from_ter, std::make_pair( to_ter, to_furn ) ) );
     } else {
         furn_str_id from_furn;
         mandatory( jo, false, "from_furn", from_furn );
-        optional( jo, false, "to_ter", to_ter );
+        optional( jo, false, "to_ter", to_ter, ter_str_id::NULL_ID() );
         mandatory( jo, false, "to_furn", to_furn );
         furn_migrations.insert( std::make_pair( from_furn, std::make_pair( to_ter, to_furn ) ) );
     }