diff --git a/reactos/win32ss/user/user32/controls/scrollbar.c b/reactos/win32ss/user/user32/controls/scrollbar.c
index b6f60f46881..2fc1eff4c1c 100644
--- a/reactos/win32ss/user/user32/controls/scrollbar.c
+++ b/reactos/win32ss/user/user32/controls/scrollbar.c
@@ -1502,7 +1502,7 @@ RealGetScrollInfo(HWND Wnd, INT SBType, LPSCROLLINFO Info)
 /*
  * @implemented
  */
-BOOL WINAPI GetScrollBarInfo(HWND hwnd, LONG idObject, LPSCROLLBARINFO info)
+BOOL WINAPI GetScrollBarInfo( _In_ HWND hwnd, _In_ LONG idObject, _Inout_ LPSCROLLBARINFO info)
 {
     BOOL Ret;
     PWND pWnd = ValidateHwnd(hwnd);