diff --git a/lcl/interfaces/qt/qtobject.inc b/lcl/interfaces/qt/qtobject.inc
index 428b00baa9..ba3c00a9e5 100644
--- a/lcl/interfaces/qt/qtobject.inc
+++ b/lcl/interfaces/qt/qtobject.inc
@@ -360,8 +360,9 @@ begin
       AForm := Screen.CustomFormsZOrdered[i];
       if (AForm.Parent=nil) and AForm.HandleAllocated and
         TQtWidget(AForm.Handle).getVisible and
-        not (AForm.FormStyle in [fsMDIChild, fsSplash]) and
-        not (AForm.BorderStyle in [bsNone]) then
+        ((not (AForm.FormStyle in [fsMDIChild, fsSplash]) and
+         not (AForm.BorderStyle = bsNone)) or
+        (csDesigning in AForm.ComponentState)) then
       begin
         States := TQtMainWindow(AForm.Handle).getWindowState;
         if not TQtMainWindow(AForm.Handle).isMinimized then
@@ -391,8 +392,9 @@ begin
       AForm := Screen.CustomFormsZOrdered[i];
       if (AForm.Parent=nil) and AForm.HandleAllocated and
         TQtWidget(AForm.Handle).getVisible and
-        not (AForm.FormStyle in [fsMDIChild, fsSplash]) and
-        not (AForm.BorderStyle in [bsNone]) then
+        ((not (AForm.FormStyle in [fsMDIChild, fsSplash]) and
+         not (AForm.BorderStyle = bsNone)) or
+        (csDesigning in AForm.ComponentState)) then
       begin
         States := TQtMainWindow(AForm.Handle).getWindowState;
         if TQtMainWindow(AForm.Handle).isMinimized then
diff --git a/lcl/interfaces/qt/qtwidgets.pas b/lcl/interfaces/qt/qtwidgets.pas
index d69599ec46..36edb3709e 100644
--- a/lcl/interfaces/qt/qtwidgets.pas
+++ b/lcl/interfaces/qt/qtwidgets.pas
@@ -3945,7 +3945,8 @@ begin
   {$IFDEF HASX11}
   if (LCLObject is TCustomForm) and EqualRect(FrameRect, WindowRect) and
     (TCustomForm(LCLObject).BorderStyle <> bsNone) and
-    not (TCustomForm(LCLObject).FormStyle in [fsMDIChild,fsSplash]) then
+    (not (TCustomForm(LCLObject).FormStyle in [fsMDIChild,fsSplash]) or
+      (csDesigning in LCLObject.ComponentState)) then
   begin
     ACurrPos := getPos;
     // do not send garbage to LCL. This window isn't decorated yet by WM.
diff --git a/lcl/interfaces/qt/qtwsforms.pp b/lcl/interfaces/qt/qtwsforms.pp
index 5d2cd7ba38..1de20c2ac7 100644
--- a/lcl/interfaces/qt/qtwsforms.pp
+++ b/lcl/interfaces/qt/qtwsforms.pp
@@ -194,7 +194,7 @@ begin
       AForm.BorderIcons, AForm.FormStyle);
   end;
 
-  if not (AForm.FormStyle in [fsMDIChild]) and
+  if (not (AForm.FormStyle in [fsMDIChild]) or (csDesigning in AForm.ComponentState)) and
      (Application <> nil) and
      (Application.MainForm <> nil) and
      (Application.MainForm.HandleAllocated) and
@@ -203,14 +203,16 @@ begin
     if (AForm.ShowInTaskBar in [stDefault, stNever])
        {$ifdef HASX11}
        {QtTool have not minimize button !}
-       and not (AForm.BorderStyle in [bsSizeToolWin, bsToolWindow])
+       and (not (AForm.BorderStyle in [bsSizeToolWin, bsToolWindow]) or
+          (csDesigning in AForm.ComponentState))
        {$endif} then
       QtMainWindow.setShowInTaskBar(False);
     if Assigned(AForm.PopupParent) then
       PopupParent := TQtWidget(AForm.PopupParent.Handle).Widget
     else
       PopupParent := nil;
-    QtMainWindow.setPopupParent(AForm.PopupMode, PopupParent);
+    if not (csDesigning in AForm.ComponentState) then
+      QtMainWindow.setPopupParent(AForm.PopupMode, PopupParent);
   end;
 
   {$IFDEF HASX11}
@@ -226,9 +228,9 @@ begin
   {$ENDIF}
   QtMainWindow.MenuBar.AttachEvents;
   
-  if (AForm.FormStyle in [fsMDIChild]) and
-     (Application.MainForm.FormStyle = fsMdiForm) and
-     not (csDesigning in AWinControl.ComponentState) then
+  if not (csDesigning in AForm.ComponentState) and
+    (AForm.FormStyle in [fsMDIChild]) and
+    (Application.MainForm.FormStyle = fsMdiForm) then
   begin
     QMdiArea_addSubWindow(
       QMdiAreaH(TQtMainWindow(Application.MainForm.Handle).MDIAreaHandle.Widget),
@@ -377,7 +379,7 @@ begin
      (Application.MainForm <> AForm) then
     Enable := false;
   {$IFDEF HASX11}
-  if AForm.FormStyle <> fsMDIChild then
+  if (AForm.FormStyle <> fsMDIChild) then
     SetSkipX11Taskbar(TQtMainWindow(AForm.Handle).Widget, not Enable);
   {$ENDIF}
   TQtMainWindow(AForm.Handle).setShowInTaskBar(Enable);
@@ -505,7 +507,8 @@ begin
       end;
     end;
 
-    if TForm(AWinControl).FormStyle <> fsMDIChild then
+    if (TForm(AWinControl).FormStyle <> fsMDIChild) or
+      (csDesigning in AWinControl.ComponentState) then
     begin
       if (csDesigning in AWinControl.ComponentState) and
         (TCustomForm(AWinControl).WindowState = wsMaximized) then