Index: reactos/sdk/include/ndk/rtltypes.h
===================================================================
--- reactos/sdk/include/ndk/rtltypes.h	(revision 75354)
+++ reactos/sdk/include/ndk/rtltypes.h	(working copy)
@@ -53,6 +53,7 @@
 #define RTL_USER_PROCESS_PARAMETERS_LOCAL_DLL_PATH          0x2000
 #define RTL_USER_PROCESS_PARAMETERS_IMAGE_KEY_MISSING       0x4000
 #define RTL_USER_PROCESS_PARAMETERS_NX                      0x20000
+#define RTL_USER_PROCESS_PARAMETERS_MASK_EXCEPTIONS         0x80000
 
 #define RTL_MAX_DRIVE_LETTERS 32
 #define RTL_DRIVE_LETTER_VALID (USHORT)0x0001
Index: reactos/win32ss/user/user32/windows/message.c
===================================================================
--- reactos/win32ss/user/user32/windows/message.c	(revision 75354)
+++ reactos/win32ss/user/user32/windows/message.c	(working copy)
@@ -1409,7 +1409,7 @@
 {
   MSG AnsiMsg;
   MSG UnicodeMsg;
-  BOOL Hook = FALSE, MsgOverride = FALSE, Dialog, DlgOverride = FALSE;
+  BOOL Hook = FALSE, MsgOverride = FALSE, Dialog, DlgOverride = FALSE, MaskExceptions;
   LRESULT Result = 0, PreResult = 0;
   DWORD Data = 0;
 
@@ -1424,6 +1424,8 @@
   else
      Dialog = FALSE;
 
+  MaskExceptions = Dialog || (NtCurrentPeb()->ProcessParameters->Flags & RTL_USER_PROCESS_PARAMETERS_MASK_EXCEPTIONS);
+
   Hook = BeginIfHookedUserApiHook();
   if (Hook)
   {
@@ -1463,7 +1465,7 @@
 
       if (PreResult) goto Exit;
 
-      if (!Dialog)
+      if (!MaskExceptions)
       Result = CALL_EXTERN_WNDPROC(WndProc, AnsiMsg.hwnd, AnsiMsg.message, AnsiMsg.wParam, AnsiMsg.lParam);
       else
       {
@@ -1473,7 +1475,7 @@
       }
       _SEH2_EXCEPT(EXCEPTION_EXECUTE_HANDLER)
       {
-         ERR("Exception Dialog Ansi %p Msg %d pti %p Wndpti %p\n",WndProc,Msg,GetW32ThreadInfo(),pWnd->head.pti);
+         ERR("Exception %s Ansi %p Msg %d pti %p Wndpti %p\n",Dialog?"Dialog":"ProcParam",WndProc,Msg,GetW32ThreadInfo(),pWnd->head.pti);
       }
       _SEH2_END;
       }
@@ -1517,7 +1519,7 @@
 
       if (PreResult) goto Exit;
 
-      if (!Dialog)
+      if (!MaskExceptions)
       Result = CALL_EXTERN_WNDPROC(WndProc, hWnd, Msg, wParam, lParam);
       else
       {
@@ -1527,7 +1529,7 @@
       }
       _SEH2_EXCEPT(EXCEPTION_EXECUTE_HANDLER)
       {
-         ERR("Exception Dialog unicode %p Msg %d pti %p Wndpti %p\n",WndProc, Msg,GetW32ThreadInfo(),pWnd->head.pti);
+         ERR("Exception %s unicode %p Msg %d pti %p Wndpti %p\n",Dialog?"Dialog":"ProcParam",WndProc, Msg,GetW32ThreadInfo(),pWnd->head.pti);
       }
       _SEH2_END;
       }
@@ -1564,7 +1566,7 @@
 {
   MSG AnsiMsg;
   MSG UnicodeMsg;
-  BOOL Hook = FALSE, MsgOverride = FALSE, Dialog, DlgOverride = FALSE;
+  BOOL Hook = FALSE, MsgOverride = FALSE, Dialog, DlgOverride = FALSE, MaskExceptions;
   LRESULT Result = 0, PreResult = 0;
   DWORD Data = 0;
 
@@ -1582,6 +1584,8 @@
   else
      Dialog = FALSE;
 
+  MaskExceptions = Dialog || (NtCurrentPeb()->ProcessParameters->Flags & RTL_USER_PROCESS_PARAMETERS_MASK_EXCEPTIONS);
+
   Hook = BeginIfHookedUserApiHook();
   if (Hook)
   {
@@ -1609,7 +1613,7 @@
 
       if (PreResult) goto Exit;
 
-      if (!Dialog)
+      if (!MaskExceptions)
       Result = CALL_EXTERN_WNDPROC(WndProc, hWnd, Msg, wParam, lParam);
       else
       {
@@ -1670,7 +1674,7 @@
 
       if (PreResult) goto Exit;
 
-      if (!Dialog)
+      if (!MaskExceptions)
       Result = CALL_EXTERN_WNDPROC(WndProc, UnicodeMsg.hwnd, UnicodeMsg.message, UnicodeMsg.wParam, UnicodeMsg.lParam);
       else
       {