diff --git a/reactos/dll/win32/user32/include/ntwrapper.h b/reactos/dll/win32/user32/include/ntwrapper.h
index 9b00ecc35b9..aa4badb92b0 100644
--- a/reactos/dll/win32/user32/include/ntwrapper.h
+++ b/reactos/dll/win32/user32/include/ntwrapper.h
@@ -85,7 +85,7 @@ RegisterTasklist(DWORD x)
 }
 
 EXTINLINE DWORD WINAPI
-DragObject(HWND hwnd1, HWND hwnd2, UINT u1, DWORD dw1, HCURSOR hc1)
+DragObject(HWND hwnd1, HWND hwnd2, UINT u1, ULONG_PTR dw1, HCURSOR hc1)
 {
     return NtUserDragObject(hwnd1, hwnd2, u1, dw1, hc1);
 }
@@ -96,7 +96,7 @@ KillTimer(HWND hWnd, UINT_PTR IDEvent)
     return NtUserKillTimer(hWnd, IDEvent);
 }
 
-EXTINLINE UINT_PTR WINAPI
+EXTINLINE UINT WINAPI // FIXME: wine compatibility definition, should be UINT_PTR
 SetSystemTimer(HWND hWnd, UINT_PTR IDEvent, UINT Period, TIMERPROC TimerFunc)
 {
     return NtUserSetSystemTimer(hWnd, IDEvent, Period, TimerFunc);
diff --git a/reactos/dll/win32/user32/include/user32p.h b/reactos/dll/win32/user32/include/user32p.h
index 7c6ba9db253..6dc7bde831f 100644
--- a/reactos/dll/win32/user32/include/user32p.h
+++ b/reactos/dll/win32/user32/include/user32p.h
@@ -118,7 +118,7 @@
   NtUserCallOneParam((DWORD)bShow, ONEPARAM_ROUTINE_SHOWCURSOR)
 
 #define NtUserGetDesktopMapping(Ptr) \
-  (PVOID)NtUserCallOneParam((DWORD)Ptr, ONEPARAM_ROUTINE_GETDESKTOPMAPPING)
+  (PVOID)NtUserCallOneParam((DWORD_PTR)Ptr, ONEPARAM_ROUTINE_GETDESKTOPMAPPING)
 
 #define ShowCaret(hwnd) \
   NtUserShowCaret(hwnd)
@@ -127,7 +127,7 @@
   NtUserHideCaret(hwnd)
 
 #define NtUserRegisterSystemClasses(Count,SysClasses) \
-    (BOOL)NtUserCallTwoParam((DWORD)Count, (DWORD)SysClasses, TWOPARAM_ROUTINE_ROS_REGSYSCLASSES)
+    (BOOL)NtUserCallTwoParam(Count, (DWORD_PTR)SysClasses, TWOPARAM_ROUTINE_ROS_REGSYSCLASSES)
 
 /* Internal Thread Data */
 extern HINSTANCE User32Instance;