diff --git a/src/network/network_gui.cpp b/src/network/network_gui.cpp
--- a/src/network/network_gui.cpp
+++ b/src/network/network_gui.cpp
@@ -794,8 +794,14 @@ public:
 		if (this->field == NGWW_CLIENT) this->HandleEditBox(NGWW_CLIENT);
 	}
 
-	virtual void OnInvalidateData(int data)
+	/**
+	 * Some data on this window has become invalid.
+	 * @param data Information about the changed data.
+	 * @param gui_scope Whether the call is done from GUI scope. You may not do everything when not in GUI scope. See #InvalidateWindowData() for details.
+	 */
+	virtual void OnInvalidateData(int data = 0, bool gui_scope = true)
 	{
+		if (!gui_scope) return;
 		if (data == 1) {
 			this->server = NULL;
 			this->list_pos = SLP_INVALID;