diff --git a/reactos/win32ss/gdi/eng/engwindow.c b/reactos/win32ss/gdi/eng/engwindow.c
index 86560c9770d..b3eecd2abc9 100644
--- a/reactos/win32ss/gdi/eng/engwindow.c
+++ b/reactos/win32ss/gdi/eng/engwindow.c
@@ -96,6 +96,7 @@ IntEngWndUpdateClipObj(
 
     /* Update the WNDOBJ */
     Clip->WndObj.rclClient = Window->rcClient;
+    Clip->WndObj.coClient.iUniq++;
 
     return TRUE;
 }
@@ -111,12 +112,6 @@ IntEngWindowChanged(
 {
     XCLIPOBJ *Clip;
 
-    /*
-     * This function is broken because AtomWndObj conflicts with
-     * properties set from user mode using SetPropW
-     */
-    return;
-
     ASSERT_IRQL_LESS_OR_EQUAL(PASSIVE_LEVEL);
 
     Clip = UserGetProp(Window, AtomWndObj);
@@ -126,7 +121,7 @@ IntEngWindowChanged(
     }
 
     ASSERT(Clip->Hwnd == Window->head.h);
-    if (Clip->WndObj.pvConsumer != NULL)
+    // if (Clip->WndObj.pvConsumer != NULL)
     {
         /* Update the WNDOBJ */
         switch (flChanged)
@@ -173,6 +168,11 @@ EngCreateWnd(
     TRACE("EngCreateWnd: pso = 0x%p, hwnd = 0x%p, pfn = 0x%p, fl = 0x%lx, pixfmt = %d\n",
             pso, hWnd, pfn, fl, iPixelFormat);
 
+    if (fl & (WO_RGN_WINDOW | WO_RGN_DESKTOP_COORD | WO_RGN_UPDATE_ALL))
+    {
+        FIXME("Unsupported flags: 0x%lx\n", fl & ~(WO_RGN_CLIENT_DELTA | WO_RGN_CLIENT | WO_RGN_SURFACE_DELTA | WO_RGN_SURFACE));
+    }
+
     calledFromUser = UserIsEntered();
     if (!calledFromUser) {
         UserEnterShared();
@@ -209,7 +209,12 @@ EngCreateWnd(
     /* Fill internal object */
     Clip->Hwnd = hWnd;
     Clip->ChangeProc = pfn;
-    Clip->Flags = fl;
+    /* Keep track of relevant flags */
+    Clip->Flags = fl & (WO_RGN_CLIENT_DELTA | WO_RGN_CLIENT | WO_RGN_SURFACE_DELTA | WO_RGN_SURFACE | WO_DRAW_NOTIFY);
+    if (fl & WO_SPRITE_NOTIFY)
+        Clip->Flags |= WOC_SPRITE_OVERLAP | WOC_SPRITE_NO_OVERLAP;
+    /* Those should always be sent */
+    Clip->Flags |= WOC_CHANGED | WOC_DELETE;
     Clip->PixelFormat = iPixelFormat;
 
     /* associate object with window */
@@ -259,8 +264,8 @@ EngDeleteWnd(
     {
         /* Remove object from window */
         IntRemoveProp(Window, AtomWndObj);
-        --gcountPWO;
     }
+    --gcountPWO;
 
     if (!calledFromUser) {
         UserLeave();
diff --git a/reactos/win32ss/gdi/ntgdi/dclife.c b/reactos/win32ss/gdi/ntgdi/dclife.c
index 67ce491a2ab..9dce67611e2 100644
--- a/reactos/win32ss/gdi/ntgdi/dclife.c
+++ b/reactos/win32ss/gdi/ntgdi/dclife.c
@@ -318,7 +318,7 @@ DC_vInitDc(
     /* Other stuff */
     pdc->hdcNext = NULL;
     pdc->hdcPrev = NULL;
-    pdc->ipfdDevMax = 0x0000ffff;
+    pdc->ipfdDevMax = 0;
     pdc->ulCopyCount = -1;
     pdc->ptlDoBanding.x = 0;
     pdc->ptlDoBanding.y = 0;
diff --git a/reactos/win32ss/gdi/ntgdi/wingl.c b/reactos/win32ss/gdi/ntgdi/wingl.c
index 7225b5d71c2..39dabbce8c4 100644
--- a/reactos/win32ss/gdi/ntgdi/wingl.c
+++ b/reactos/win32ss/gdi/ntgdi/wingl.c
@@ -62,7 +62,19 @@ NtGdiDescribePixelFormat(
     }
 
     if (!pdc->ipfdDevMax)
-        IntGetipfdDevMax(pdc);
+    {
+        if (!IntGetipfdDevMax(pdc))
+        {
+            /* EngSetLastError ? */
+            goto Exit;
+        }
+    }
+
+    if (!ppfd)
+    {
+        Ret = pdc->ipfdDevMax;
+        goto Exit;
+    }
 
     if ((ipfd < 1) || (ipfd > pdc->ipfdDevMax))
     {
diff --git a/reactos/win32ss/user/ntuser/ntuser.c b/reactos/win32ss/user/ntuser/ntuser.c
index f496e420a15..7b3a4bc5666 100644
--- a/reactos/win32ss/user/ntuser/ntuser.c
+++ b/reactos/win32ss/user/ntuser/ntuser.c
@@ -49,7 +49,12 @@ InitUserAtoms(VOID)
 
   gpsi->atomFrostedWindowProp = IntAddGlobalAtom(L"SysFrostedWindow", TRUE);
 
-  AtomWndObj = IntAddGlobalAtom(L"SysWNDO", TRUE);
+  /*
+   * FIXME: AddPropW uses the global kernel atom table, thus leading to conflicts if we use
+   * the win32k atom table for this ones. What is the right thing to do ?
+   */
+  // AtomWndObj = IntAddGlobalAtom(L"SysWNDO", TRUE);
+  NtAddAtom(L"SysWNDO", 14, &AtomWndObj);
   AtomLayer = IntAddGlobalAtom(L"SysLayer", TRUE);
   AtomFlashWndState = IntAddGlobalAtom(L"FlashWState", TRUE);
 
diff --git a/reactos/win32ss/user/ntuser/windc.c b/reactos/win32ss/user/ntuser/windc.c
index 5ff495c9950..0e712672731 100644
--- a/reactos/win32ss/user/ntuser/windc.c
+++ b/reactos/win32ss/user/ntuser/windc.c
@@ -276,11 +276,9 @@ noparent:
 
    Dce->DCXFlags &= ~DCX_DCEDIRTY;
    GdiSelectVisRgn(Dce->hDC, RgnVisible);
-
-   if (VerifyWnd(Window)) // Window maybe dead by this time before finishing the DCE release.
-   {
-      IntEngWindowChanged(Window, WOC_RGN_CLIENT);
-   }
+   /* Tell GDI driver */
+   if (Window)
+       IntEngWindowChanged(Window, WOC_RGN_CLIENT);
 
    if (RgnVisible != NULL)
    {
@@ -935,12 +933,6 @@ DceResetActiveDCEs(PWND Window)
 
          DceUpdateVisRgn(pDCE, CurrentWindow, pDCE->DCXFlags);
          IntGdiSetHookFlags(pDCE->hDC, DCHF_VALIDATEVISRGN);
-
-         if (Window->head.h != pDCE->hwndCurrent)
-         {
-//            IntEngWindowChanged(CurrentWindow, WOC_RGN_CLIENT);
-//            UserDerefObject(CurrentWindow);
-         }
       }
       pLE = pDCE->List.Flink;
       pDCE = CONTAINING_RECORD(pLE, DCE, List);