diff --git a/reactos/include/psdk/winnt.h b/reactos/include/psdk/winnt.h
index 586f09c6ef0..6a96e9f1aaa 100644
--- a/reactos/include/psdk/winnt.h
+++ b/reactos/include/psdk/winnt.h
@@ -4438,7 +4438,11 @@ static __inline__ PVOID GetCurrentFiber(void)
 #elif defined (_M_AMD64)
 FORCEINLINE PVOID GetCurrentFiber(VOID)
 {
+  #ifdef NONAMELESSUNION
+    return (PVOID)__readgsqword(FIELD_OFFSET(NT_TIB, DUMMYUNIONNAME.FiberData));
+  #else
     return (PVOID)__readgsqword(FIELD_OFFSET(NT_TIB, FiberData));
+  #endif
 }
 #elif defined (_M_ARM)
     PVOID WINAPI GetCurrentFiber(VOID);
diff --git a/reactos/include/psdk/winuser.h b/reactos/include/psdk/winuser.h
index 435f7f9ffcb..437316bb8d7 100644
--- a/reactos/include/psdk/winuser.h
+++ b/reactos/include/psdk/winuser.h
@@ -3709,12 +3709,12 @@ BOOL WINAPI DestroyWindow(HWND);
 #define DialogBoxW(i,t,p,f) DialogBoxParamW(i,t,p,f,0)
 #define DialogBoxIndirectA(i,t,p,f) DialogBoxIndirectParamA(i,t,p,f,0)
 #define DialogBoxIndirectW(i,t,p,f) DialogBoxIndirectParamW(i,t,p,f,0)
-int WINAPI DialogBoxIndirectParamA(HINSTANCE,LPCDLGTEMPLATE,HWND,DLGPROC,LPARAM);
-int WINAPI DialogBoxIndirectParamW(HINSTANCE,LPCDLGTEMPLATE,HWND,DLGPROC,LPARAM);
-int WINAPI DialogBoxParamA(HINSTANCE,LPCSTR,HWND,DLGPROC,LPARAM);
-int WINAPI DialogBoxParamW(HINSTANCE,LPCWSTR,HWND,DLGPROC,LPARAM);
-LONG WINAPI DispatchMessageA(const MSG*);
-LONG WINAPI DispatchMessageW(const MSG*);
+INT_PTR WINAPI DialogBoxIndirectParamA(HINSTANCE,LPCDLGTEMPLATE,HWND,DLGPROC,LPARAM);
+INT_PTR WINAPI DialogBoxIndirectParamW(HINSTANCE,LPCDLGTEMPLATE,HWND,DLGPROC,LPARAM);
+INT_PTR WINAPI DialogBoxParamA(HINSTANCE,LPCSTR,HWND,DLGPROC,LPARAM);
+INT_PTR WINAPI DialogBoxParamW(HINSTANCE,LPCWSTR,HWND,DLGPROC,LPARAM);
+LRESULT WINAPI DispatchMessageA(const MSG*);
+LRESULT WINAPI DispatchMessageW(const MSG*);
 int WINAPI DlgDirListA(HWND,LPSTR,int,int,UINT);
 int WINAPI DlgDirListW(HWND,LPWSTR,int,int,UINT);
 int WINAPI DlgDirListComboBoxA(HWND,LPSTR,int,int,UINT);
@@ -3747,7 +3747,7 @@ BOOL WINAPI EnableMenuItem(HMENU,UINT,UINT);
 BOOL WINAPI EnableScrollBar(HWND,UINT,UINT);
 BOOL WINAPI EnableWindow(HWND,BOOL);
 BOOL WINAPI EndDeferWindowPos(HDWP);
-BOOL WINAPI EndDialog(HWND,int);
+BOOL WINAPI EndDialog(HWND,INT_PTR);
 BOOL WINAPI EndMenu(void);
 BOOL WINAPI EndPaint(HWND,const PAINTSTRUCT*);
 #if (_WIN32_WINNT >= 0x0500)
@@ -3804,8 +3804,8 @@ BOOL WINAPI GetClassInfoExW(HINSTANCE,LPCWSTR,LPWNDCLASSEXW);
 DWORD WINAPI GetClassLongA(HWND,int);
 DWORD WINAPI GetClassLongW(HWND,int);
 #ifdef _WIN64
-LONG_PTR WINAPI GetClassLongPtrA(HWND,int);
-LONG_PTR WINAPI GetClassLongPtrW(HWND,int);
+ULONG_PTR WINAPI GetClassLongPtrA(HWND,int);
+ULONG_PTR WINAPI GetClassLongPtrW(HWND,int);
 #else
 #define GetClassLongPtrA GetClassLongA
 #define GetClassLongPtrW GetClassLongW
@@ -3866,7 +3866,7 @@ int WINAPI GetMenuStringA(HMENU,UINT,LPSTR,int,UINT);
 int WINAPI GetMenuStringW(HMENU,UINT,LPWSTR,int,UINT);
 BOOL WINAPI GetMessageA(LPMSG,HWND,UINT,UINT);
 BOOL WINAPI GetMessageW(LPMSG,HWND,UINT,UINT);
-LONG WINAPI GetMessageExtraInfo(void);
+LPARAM WINAPI GetMessageExtraInfo(void);
 DWORD WINAPI GetMessagePos(void);
 LONG WINAPI GetMessageTime(void);
 #if (_WIN32_WINNT >= 0x0500 || _WIN32_WINDOWS >= 0x0490)
@@ -4001,8 +4001,8 @@ BOOL WINAPI IsWindowVisible(HWND);
 BOOL WINAPI IsWinEventHookInstalled(DWORD);
 #endif
 BOOL WINAPI IsZoomed(HWND);
-VOID WINAPI keybd_event(BYTE,BYTE,DWORD,DWORD);
-BOOL WINAPI KillTimer(HWND,UINT);
+VOID WINAPI keybd_event(BYTE,BYTE,DWORD,ULONG_PTR);
+BOOL WINAPI KillTimer(HWND,UINT_PTR);
 HACCEL WINAPI LoadAcceleratorsA(HINSTANCE,LPCSTR);
 HACCEL WINAPI LoadAcceleratorsW(HINSTANCE,LPCWSTR);
 HBITMAP WINAPI LoadBitmapA(HINSTANCE,LPCSTR);
@@ -4114,16 +4114,16 @@ BOOL WINAPI ScreenToClient(HWND,LPPOINT);
 BOOL WINAPI ScrollDC(HDC,int,int,LPCRECT,LPCRECT,HRGN,LPRECT);
 BOOL WINAPI ScrollWindow(HWND,int,int,LPCRECT,LPCRECT);
 int WINAPI ScrollWindowEx(HWND,int,int,LPCRECT,LPCRECT,HRGN,LPRECT,UINT);
-LONG WINAPI SendDlgItemMessageA(HWND,int,UINT,WPARAM,LPARAM);
-LONG WINAPI SendDlgItemMessageW(HWND,int,UINT,WPARAM,LPARAM);
+LRESULT WINAPI SendDlgItemMessageA(HWND,int,UINT,WPARAM,LPARAM);
+LRESULT WINAPI SendDlgItemMessageW(HWND,int,UINT,WPARAM,LPARAM);
 #if (_WIN32_WINNT >= 0x0403)
 UINT WINAPI SendInput(UINT,LPINPUT,int);
 #endif
 LRESULT WINAPI SendMessageA(HWND,UINT,WPARAM,LPARAM);
-BOOL WINAPI SendMessageCallbackA(HWND,UINT,WPARAM,LPARAM,SENDASYNCPROC,DWORD);
-BOOL WINAPI SendMessageCallbackW(HWND,UINT,WPARAM,LPARAM,SENDASYNCPROC,DWORD);
-LRESULT WINAPI SendMessageTimeoutA(HWND,UINT,WPARAM,LPARAM,UINT,UINT,PDWORD);
-LRESULT WINAPI SendMessageTimeoutW(HWND,UINT,WPARAM,LPARAM,UINT,UINT,PDWORD);
+BOOL WINAPI SendMessageCallbackA(HWND,UINT,WPARAM,LPARAM,SENDASYNCPROC,ULONG_PTR);
+BOOL WINAPI SendMessageCallbackW(HWND,UINT,WPARAM,LPARAM,SENDASYNCPROC,ULONG_PTR);
+LRESULT WINAPI SendMessageTimeoutA(HWND,UINT,WPARAM,LPARAM,UINT,UINT,PDWORD_PTR);
+LRESULT WINAPI SendMessageTimeoutW(HWND,UINT,WPARAM,LPARAM,UINT,UINT,PDWORD_PTR);
 LRESULT WINAPI SendMessageW(HWND,UINT,WPARAM,LPARAM);
 BOOL WINAPI SendNotifyMessageA(HWND,UINT,WPARAM,LPARAM);
 BOOL WINAPI SendNotifyMessageW(HWND,UINT,WPARAM,LPARAM);
@@ -4179,7 +4179,7 @@ HANDLE WINAPI SetSysColorsTemp(const COLORREF *, const HBRUSH *, int);
 #define SetSysModalWindow(h) (NULL)
 BOOL WINAPI SetSystemCursor(HCURSOR,DWORD);
 BOOL WINAPI SetThreadDesktop(HDESK);
-UINT WINAPI SetTimer(HWND,UINT,UINT,TIMERPROC);
+UINT_PTR WINAPI SetTimer(HWND,UINT_PTR,UINT,TIMERPROC);
 BOOL WINAPI SetUserObjectInformationA(HANDLE,int,PVOID,DWORD);
 BOOL WINAPI SetUserObjectInformationW(HANDLE,int,PVOID,DWORD);
 BOOL WINAPI SetUserObjectSecurity(HANDLE,PSECURITY_INFORMATION,PSECURITY_DESCRIPTOR);