diff --git a/win32ss/user/ntuser/defwnd.c b/win32ss/user/ntuser/defwnd.c
index 67215d1f26d..fc55c4acfba 100644
--- a/win32ss/user/ntuser/defwnd.c
+++ b/win32ss/user/ntuser/defwnd.c
@@ -787,6 +787,11 @@ IntDefWindowProc(
             PWND topWnd = UserGetWindowObject(hwndTop);
             if (topWnd)
             {
+               if ((topWnd->style & WS_THICKFRAME) == 0)
+               {
+                  return 0;
+               }
+               
                if (wParam == VK_DOWN)
                {
                    if (topWnd->style & WS_MAXIMIZE)
diff --git a/win32ss/user/ntuser/nonclient.c b/win32ss/user/ntuser/nonclient.c
index 7a5fcc445e8..ba8dececb13 100644
--- a/win32ss/user/ntuser/nonclient.c
+++ b/win32ss/user/ntuser/nonclient.c
@@ -395,7 +395,7 @@ DefWndDoSizeMove(PWND pwnd, WORD wParam)
       if (msg.message == WM_LBUTTONUP)
       {
          // check for snapping if was moved by caption
-         if (hittest == HTCAPTION)
+         if (hittest == HTCAPTION && thickframe && (ExStyle & WS_EX_MDICHILD) == 0)
          {
             RECT snapRect;
             BOOL doSideSnap = FALSE;
@@ -1618,6 +1618,10 @@ NC_HandleNCLButtonDblClk(PWND pWnd, WPARAM wParam, LPARAM lParam)
     case HTBOTTOM:
     {
       RECT sizingRect = pWnd->rcWindow, mouseRect;
+      
+      if (pWnd->ExStyle & WS_EX_MDICHILD)
+          break;
+      
       UserSystemParametersInfo(SPI_GETWORKAREA, 0, &mouseRect, 0);
         
       co_WinPosSetWindowPos(pWnd,