diff --git a/include/wx/treebase.h b/include/wx/treebase.h
index d6accc47d4..fe2cb9135b 100644
--- a/include/wx/treebase.h
+++ b/include/wx/treebase.h
@@ -61,7 +61,7 @@ public:
 
 #if WXWIN_COMPATIBILITY_2_4
     // deprecated: only for compatibility, don't work on 64 bit archs
-    wxTreeItemId(long item) { wxULongToPtr(m_pItem, item); }
+    wxTreeItemId(long item) { m_pItem = wxUIntToPtr(item); }
     operator long() const { return (long)wxPtrToUInt(m_pItem); }
 #else // !WXWIN_COMPATIBILITY_2_4
     operator bool() const { return IsOk(); }