diff --git a/dbconverter/src/main.h b/dbconverter/src/main.h
index ccde6b20e..1206928b4 100644
--- a/dbconverter/src/main.h
+++ b/dbconverter/src/main.h
@@ -4,6 +4,7 @@
 #include "../../cockatrice/src/database/card_database.h"
 #include "../../cockatrice/src/database/parser/cockatrice_xml_4.h"
 
+class CardDatabaseQuerier;
 class CardDatabaseConverter : public CardDatabase
 {
 public: