diff --git a/src/network/network_command.cpp b/src/network/network_command.cpp
--- a/src/network/network_command.cpp
+++ b/src/network/network_command.cpp
@@ -332,7 +332,7 @@ void NetworkGameSocketHandler::SendComma
 	}
 
 	if (callback == lengthof(_callback_table)) {
-		DEBUG(net, 0, "Unknown callback for command; no callback sent (command: %d)", cp->cmd);
+		Debug(net, 0, "Unknown callback for command; no callback sent (command: {})", cp->cmd);
 		callback = 0; // _callback_table[0] == nullptr
 	}
 	p->Send_uint8 (callback);