diff --git a/src/error_gui.cpp b/src/error_gui.cpp
index 812e04cefa..412864226c 100644
--- a/src/error_gui.cpp
+++ b/src/error_gui.cpp
@@ -348,7 +348,7 @@ void ShowFirstError()
  */
 void UnshowCriticalError()
 {
-	ErrmsgWindow *w = (ErrmsgWindow*)FindWindowById(WC_ERRMSG, 0);
+	ErrmsgWindow *w = dynamic_cast<ErrmsgWindow *>(FindWindowById(WC_ERRMSG, 0));
 	if (_window_system_initialized && w != nullptr) {
 		if (w->IsCritical()) _error_list.push_front(*w);
 		_window_system_initialized = false;
@@ -414,7 +414,7 @@ void ShowErrorMessage(StringID summary_msg, StringID detailed_msg, WarningLevel
 	ErrorMessageData data(summary_msg, detailed_msg, is_critical, x, y, textref_stack_grffile, textref_stack_size, textref_stack, extra_msg);
 	data.CopyOutDParams();
 
-	ErrmsgWindow *w = (ErrmsgWindow*)FindWindowById(WC_ERRMSG, 0);
+	ErrmsgWindow *w = dynamic_cast<ErrmsgWindow *>(FindWindowById(WC_ERRMSG, 0));
 	if (w != nullptr) {
 		if (w->IsCritical()) {
 			/* A critical error is currently shown. */
@@ -438,7 +438,7 @@ void ShowErrorMessage(StringID summary_msg, StringID detailed_msg, WarningLevel
  */
 bool HideActiveErrorMessage()
 {
-	ErrmsgWindow *w = (ErrmsgWindow*)FindWindowById(WC_ERRMSG, 0);
+	ErrmsgWindow *w = dynamic_cast<ErrmsgWindow *>(FindWindowById(WC_ERRMSG, 0));
 	if (w == nullptr) return false;
 	w->Close();
 	return true;
diff --git a/src/group_gui.cpp b/src/group_gui.cpp
index 1143de9f0f..55bb30dd1e 100644
--- a/src/group_gui.cpp
+++ b/src/group_gui.cpp
@@ -1169,7 +1169,7 @@ void ShowCompanyGroupForVehicle(const Vehicle *v)
  */
 static inline VehicleGroupWindow *FindVehicleGroupWindow(VehicleType vt, Owner owner)
 {
-	return (VehicleGroupWindow *)FindWindowById(GetWindowClassForVehicleType(vt), VehicleListIdentifier(VL_GROUP_LIST, vt, owner).Pack());
+	return dynamic_cast<VehicleGroupWindow *>(FindWindowById(GetWindowClassForVehicleType(vt), VehicleListIdentifier(VL_GROUP_LIST, vt, owner).Pack()));
 }
 
 /**
diff --git a/src/network/network_gui.cpp b/src/network/network_gui.cpp
index b659f64d21..aa9940c936 100644
--- a/src/network/network_gui.cpp
+++ b/src/network/network_gui.cpp
@@ -2234,7 +2234,7 @@ void ShowJoinStatusWindow()
 
 void ShowNetworkNeedPassword(NetworkPasswordType npt, std::shared_ptr<NetworkAuthenticationPasswordRequest> request)
 {
-	NetworkJoinStatusWindow *w = (NetworkJoinStatusWindow *)FindWindowById(WC_NETWORK_STATUS_WINDOW, WN_NETWORK_STATUS_WINDOW_JOIN);
+	NetworkJoinStatusWindow *w = dynamic_cast<NetworkJoinStatusWindow *>(FindWindowById(WC_NETWORK_STATUS_WINDOW, WN_NETWORK_STATUS_WINDOW_JOIN));
 	if (w == nullptr) return;
 	w->request = request;
 
diff --git a/src/news_gui.cpp b/src/news_gui.cpp
index fe7710ca8d..e90772f170 100644
--- a/src/news_gui.cpp
+++ b/src/news_gui.cpp
@@ -1017,7 +1017,7 @@ static void ShowNewsMessage(NewsIterator ni)
  */
 bool HideActiveNewsMessage()
 {
-	NewsWindow *w = (NewsWindow*)FindWindowById(WC_NEWS_WINDOW, 0);
+	NewsWindow *w = dynamic_cast<NewsWindow *>(FindWindowById(WC_NEWS_WINDOW, 0));
 	if (w == nullptr) return false;
 	w->Close();
 	return true;