diff --git a/lcl/interfaces/win32/win32callback.inc b/lcl/interfaces/win32/win32callback.inc
index 0735304087..d640aea567 100644
--- a/lcl/interfaces/win32/win32callback.inc
+++ b/lcl/interfaces/win32/win32callback.inc
@@ -727,6 +727,32 @@ Var
     Windows.SendMessage(spinHandle, UDM_SETPOS32, 0, 500);
     WindowInfo^.spinValue := newValue;
   end;
+  
+  procedure SetMinMaxInfo(var MinMaxInfo: TMINMAXINFO);
+    procedure SetWin32SizePoint(AWidth, AHeight: integer; var pt: TPoint);
+    var
+      IntfWidth, IntfHeight: integer;
+    begin
+      // 0 means no constraint
+      if (AWidth=0) and (AHeight=0) then exit;
+      
+      IntfWidth := AWidth;
+      IntfHeight := AHeight;
+      LCLFormSizeToWin32Size(TCustomForm(lWinControl), IntfWidth, IntfHeight);
+
+      if AWidth>0 then
+        pt.X:= IntfWidth;
+      if AHeight>0 then
+        pt.Y := IntfHeight;
+    end;
+  begin
+    if (lWinControl=nil) or not (lWinControl is TCustomForm) then exit;
+    with lWinControl.Constraints do begin
+      SetWin32SizePoint(MinWidth, MinHeight, MinMaxInfo.ptMinTrackSize);
+      SetWin32SizePoint(MaxWidth, MaxHeight, MinMaxInfo.ptMaxSize);
+      SetWin32SizePoint(MaxWidth, MaxHeight, MinMaxInfo.ptMaxTrackSize);
+    end;
+  end;
     
 Begin
   Assert(False, 'Trace:WindowProc - Start');
@@ -1142,6 +1168,10 @@ Begin
       end;
     end;
 }
+    WM_GETMINMAXINFO:
+    begin
+      SetMinMaxInfo(PMINMAXINFO(LParam)^);
+    end;
     WM_KEYDOWN:
     Begin
       NotifyUserInput := True;
diff --git a/lcl/interfaces/win32/win32def.pp b/lcl/interfaces/win32/win32def.pp
index d1098762ea..1aa324362c 100644
--- a/lcl/interfaces/win32/win32def.pp
+++ b/lcl/interfaces/win32/win32def.pp
@@ -37,6 +37,7 @@ Const
   MCM_FIRST = $1000;
   MCM_GETCURSEL = MCM_FIRST + 1;
   MCM_SETCURSEL =  MCM_FIRST + 2;
+  MCM_GETMINREQRECT = MCM_FIRST + 9;
 
 Type
   TGDIType = (gdiBitmap, gdiBrush, gdiFont, gdiPen, gdiRegion);
diff --git a/lcl/interfaces/win32/win32proc.pp b/lcl/interfaces/win32/win32proc.pp
index 2d6b9c9e83..841f0f1d2d 100644
--- a/lcl/interfaces/win32/win32proc.pp
+++ b/lcl/interfaces/win32/win32proc.pp
@@ -27,7 +27,7 @@ unit win32proc;
 interface
 
 uses
-  Windows, Classes, LMessages, LCLType, LCLProc, Controls;
+  Windows, Classes, LMessages, LCLType, LCLProc, Controls, Forms;
 
 Type
   TEventType = (etNotify, etKey, etKeyPress, etMouseWheel, etMouseUpDown);
@@ -82,12 +82,15 @@ function GetLCLClientBoundsOffset(Sender: TObject; var ORect: TRect): boolean;
 function GetLCLClientBoundsOffset(Handle: HWnd; var Rect: TRect): boolean;
 Procedure LCLBoundsToWin32Bounds(Sender: TObject;
   var Left, Top, Width, Height: Integer);
+Procedure LCLFormSizeToWin32Size(Form: TCustomForm; var AWidth, AHeight: Integer);
 Procedure Win32PosToLCLPos(Sender: TObject; var Left, Top: SmallInt);
 procedure GetWin32ControlPos(Window, Parent: HWND; var Left, Top: integer);
 
 procedure UpdateWindowStyle(Handle: HWnd; Style: integer; StyleMask: integer);
 function BorderStyleToWin32Flags(Style: TFormBorderStyle): DWORD;
 function BorderStyleToWin32FlagsEx(Style: TFormBorderStyle): DWORD;
+function GetDesigningBorderStyle(const AForm: TCustomForm): TFormBorderStyle;
+
 function GetFileVersion(FileName: string): dword;
 function AllocWindowInfo(Window: HWND): PWindowInfo;
 function DisposeWindowInfo(Window: HWND): boolean;
@@ -115,7 +118,7 @@ var
 implementation
 
 uses
-  SysUtils, LCLStrConsts, Menus, Dialogs, StdCtrls, ExtCtrls, Forms,
+  SysUtils, LCLStrConsts, Menus, Dialogs, StdCtrls, ExtCtrls,
   LCLIntf; //remove this unit when GetWindowSize is moved to TWSWinControl
 
 {$IFOPT C-}
@@ -858,6 +861,26 @@ Begin
   inc(Top, ORect.Top);
 End;
 
+procedure LCLFormSizeToWin32Size(Form: TCustomForm; var AWidth, AHeight: Integer);
+{$NOTE Should be moved to WSWin32Forms, if the windowproc is splitted}
+var
+  SizeRect: Windows.RECT;
+  BorderStyle: TFormBorderStyle;
+begin
+  with SizeRect do
+  begin
+    Left := 0;
+    Top := 0;
+    Right := AWidth;
+    Bottom := AHeight;
+  end;
+  BorderStyle := GetDesigningBorderStyle(Form);
+  Windows.AdjustWindowRectEx(@SizeRect, BorderStyleToWin32Flags(
+      BorderStyle), false, BorderStyleToWin32FlagsEx(BorderStyle));
+  AWidth := SizeRect.Right - SizeRect.Left;
+  AHeight := SizeRect.Bottom - SizeRect.Top;
+end;
+
 Procedure Win32PosToLCLPos(Sender: TObject; var Left, Top: SmallInt);
 var
   ORect: TRect;
@@ -922,6 +945,15 @@ begin
   end;
 end;
 
+function GetDesigningBorderStyle(const AForm: TCustomForm): TFormBorderStyle;
+{$NOTE Belongs in Win32WSForms, but is needed in windowproc}
+begin
+  if csDesigning in AForm.ComponentState then
+    Result := bsSizeable
+  else
+    Result := AForm.BorderStyle;
+end;
+
 function GetFileVersion(FileName: string): dword;
 var
   buf: pointer;
diff --git a/lcl/interfaces/win32/win32wscalendar.pp b/lcl/interfaces/win32/win32wscalendar.pp
index 7a38141bd8..8c6e9f5b5a 100644
--- a/lcl/interfaces/win32/win32wscalendar.pp
+++ b/lcl/interfaces/win32/win32wscalendar.pp
@@ -85,11 +85,6 @@ begin
   SetBounds(AWinControl, Params.Left, Params.Top, 0, 0);
 end;
 
-const
-  // TODO: needs to move
-  MCM_FIRST             = $1000;
-  MCM_GETMINREQRECT     = MCM_FIRST + 9;
-      
 procedure TWin32WSCustomCalendar.AdaptBounds(const AWinControl: TWinControl;
   var Left, Top, Width, Height: integer; var SuppressMove: boolean);
 var
diff --git a/lcl/interfaces/win32/win32wsforms.pp b/lcl/interfaces/win32/win32wsforms.pp
index 3fcb0db0e1..ad7db97e34 100644
--- a/lcl/interfaces/win32/win32wsforms.pp
+++ b/lcl/interfaces/win32/win32wsforms.pp
@@ -172,14 +172,6 @@ end;
 
 { TWin32WSCustomForm }
 
-function GetDesigningBorderStyle(const AForm: TCustomForm): TFormBorderStyle;
-begin
-  if csDesigning in AForm.ComponentState then
-    Result := bsSizeable
-  else
-    Result := AForm.BorderStyle;
-end;
-
 function CalcBorderIconsFlags(const AForm: TCustomForm): dword;
 var
   BorderIcons: TBorderIcons;