diff --git a/src/network/core/tcp_game.cpp b/src/network/core/tcp_game.cpp
index 03f0de64e3..be0ffa9d9c 100644
--- a/src/network/core/tcp_game.cpp
+++ b/src/network/core/tcp_game.cpp
@@ -15,6 +15,7 @@
 #include "../network_internal.h"
 #include "../../debug.h"
 #include "../../error.h"
+#include "../../window_func.h"
 
 #include "table/strings.h"
 
@@ -109,6 +110,7 @@ NetworkRecvStatus NetworkGameSocketHandler::CloseConnection(bool error)
 	if (!_network_server && _networking) {
 		extern void ClientNetworkEmergencySave(); // from network_client.cpp
 		ClientNetworkEmergencySave();
+		DeleteNetworkClientWindows();
 		_switch_mode = SM_MENU;
 		_networking = false;
 		ShowErrorMessage(STR_NETWORK_ERROR_LOSTCONNECTION, INVALID_STRING_ID, WL_CRITICAL);
diff --git a/src/network/network_chat_gui.cpp b/src/network/network_chat_gui.cpp
index 7f8b2b2b99..447bd25c9b 100644
--- a/src/network/network_chat_gui.cpp
+++ b/src/network/network_chat_gui.cpp
@@ -522,7 +522,7 @@ static const NWidgetPart _nested_chat_window_widgets[] = {
 static WindowDesc _chat_window_desc(
 	WDP_MANUAL, nullptr, 0, 0,
 	WC_SEND_NETWORK_MSG, WC_NONE,
-	0,
+	WDF_NETWORK,
 	_nested_chat_window_widgets, lengthof(_nested_chat_window_widgets)
 );
 
diff --git a/src/network/network_client.cpp b/src/network/network_client.cpp
index e299732580..a990d75010 100644
--- a/src/network/network_client.cpp
+++ b/src/network/network_client.cpp
@@ -257,6 +257,7 @@ void ClientNetworkGameSocketHandler::ClientError(NetworkRecvStatus res)
 		ClientNetworkEmergencySave();
 	}
 
+	DeleteNetworkClientWindows();
 	_switch_mode = SM_MENU;
 	_networking = false;
 }
diff --git a/src/network/network_gui.cpp b/src/network/network_gui.cpp
index 90de6d69b0..7768e87c9e 100644
--- a/src/network/network_gui.cpp
+++ b/src/network/network_gui.cpp
@@ -1016,7 +1016,7 @@ static const NWidgetPart _nested_network_game_widgets[] = {
 static WindowDesc _network_game_window_desc(
 	WDP_CENTER, "list_servers", 1000, 730,
 	WC_NETWORK_WINDOW, WC_NONE,
-	0,
+	WDF_NETWORK,
 	_nested_network_game_widgets, lengthof(_nested_network_game_widgets)
 );
 
@@ -1289,7 +1289,7 @@ static const NWidgetPart _nested_network_start_server_window_widgets[] = {
 static WindowDesc _network_start_server_window_desc(
 	WDP_CENTER, nullptr, 0, 0,
 	WC_NETWORK_WINDOW, WC_NONE,
-	0,
+	WDF_NETWORK,
 	_nested_network_start_server_window_widgets, lengthof(_nested_network_start_server_window_widgets)
 );
 
@@ -1366,7 +1366,7 @@ static const NWidgetPart _nested_client_list_widgets[] = {
 static WindowDesc _client_list_desc(
 	WDP_AUTO, "list_clients", 220, 300,
 	WC_CLIENT_LIST, WC_NONE,
-	0,
+	WDF_NETWORK,
 	_nested_client_list_widgets, lengthof(_nested_client_list_widgets)
 );
 
@@ -2259,7 +2259,7 @@ static const NWidgetPart _nested_network_join_status_window_widgets[] = {
 static WindowDesc _network_join_status_window_desc(
 	WDP_CENTER, nullptr, 0, 0,
 	WC_NETWORK_STATUS_WINDOW, WC_NONE,
-	WDF_MODAL,
+	WDF_MODAL | WDF_NETWORK,
 	_nested_network_join_status_window_widgets, lengthof(_nested_network_join_status_window_widgets)
 );
 
@@ -2382,7 +2382,7 @@ static const NWidgetPart _nested_network_company_password_window_widgets[] = {
 static WindowDesc _network_company_password_window_desc(
 	WDP_AUTO, nullptr, 0, 0,
 	WC_COMPANY_PASSWORD_WINDOW, WC_NONE,
-	0,
+	WDF_NETWORK,
 	_nested_network_company_password_window_widgets, lengthof(_nested_network_company_password_window_widgets)
 );
 
@@ -2484,7 +2484,7 @@ static const NWidgetPart _nested_network_ask_relay_widgets[] = {
 static WindowDesc _network_ask_relay_desc(
 	WDP_CENTER, nullptr, 0, 0,
 	WC_NETWORK_ASK_RELAY, WC_NONE,
-	WDF_MODAL,
+	WDF_MODAL | WDF_NETWORK,
 	_nested_network_ask_relay_widgets, lengthof(_nested_network_ask_relay_widgets)
 );
 
diff --git a/src/window.cpp b/src/window.cpp
index cef50f2531..09eef73f2f 100644
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -3510,6 +3510,19 @@ void DeleteConstructionWindows()
 	}
 }
 
+/**
+ * Delete all windows that use network client functionality.
+ */
+void DeleteNetworkClientWindows()
+{
+	/* Note: the container remains stable, even when deleting windows. */
+	for (const Window *w : Window::IterateUnordered()) {
+		if (w->window_desc->flags & WDF_NETWORK) {
+			delete w;
+		}
+	}
+}
+
 /** Delete all always on-top windows to get an empty screen */
 void HideVitalWindows()
 {
diff --git a/src/window_func.h b/src/window_func.h
index c16d041073..9dccbd56ed 100644
--- a/src/window_func.h
+++ b/src/window_func.h
@@ -40,6 +40,7 @@ void DeleteNonVitalWindows();
 void DeleteAllNonVitalWindows();
 void DeleteAllMessages();
 void DeleteConstructionWindows();
+void DeleteNetworkClientWindows();
 void HideVitalWindows();
 void ShowVitalWindows();
 
diff --git a/src/window_gui.h b/src/window_gui.h
index f160db4c92..1153881b5b 100644
--- a/src/window_gui.h
+++ b/src/window_gui.h
@@ -229,6 +229,7 @@ enum WindowDefaultFlag {
 	WDF_CONSTRUCTION    =   1 << 0, ///< This window is used for construction; close it whenever changing company.
 	WDF_MODAL           =   1 << 1, ///< The window is a modal child of some other window, meaning the parent is 'inactive'
 	WDF_NO_FOCUS        =   1 << 2, ///< This window won't get focus/make any other window lose focus when click
+	WDF_NETWORK         =   1 << 3, ///< This window is used for network client functionality
 };
 
 /**