diff --git a/src/network/network_server.h b/src/network/network_server.h
--- a/src/network/network_server.h
+++ b/src/network/network_server.h
@@ -93,7 +93,7 @@ public:
 	NetworkRecvStatus SendMove(ClientID client_id, CompanyID company_id);
 
 	NetworkRecvStatus SendClientInfo(NetworkClientInfo *ci);
-	NetworkRecvStatus SendError(NetworkErrorCode error, const char *reason = nullptr);
+	NetworkRecvStatus SendError(NetworkErrorCode error, const std::string &reason = {});
 	NetworkRecvStatus SendChat(NetworkAction action, ClientID client_id, bool self_send, const std::string &msg, int64 data);
 	NetworkRecvStatus SendJoin(ClientID client_id);
 	NetworkRecvStatus SendFrame();