diff --git a/contrib/src/gizmos/splittree.cpp b/contrib/src/gizmos/splittree.cpp
index 87b3668ffd..df95c09d8c 100644
--- a/contrib/src/gizmos/splittree.cpp
+++ b/contrib/src/gizmos/splittree.cpp
@@ -236,7 +236,7 @@ void wxRemotelyScrolledTreeCtrl::ScrollToLine(int WXUNUSED(posHoriz), int posVer
     {
         UINT sbCode = SB_THUMBPOSITION;
         HWND vertScrollBar = 0;
-        MSWDefWindowProc((WXUINT) WM_VSCROLL, MAKELONG(sbCode, posVert), (WXHWND) vertScrollBar);
+        MSWDefWindowProc((WXUINT) WM_VSCROLL, MAKELONG(sbCode, posVert), (WXLPARAM) vertScrollBar);
     }
 #if USE_GENERIC_TREECTRL
     else