diff --git a/src/html/chm.cpp b/src/html/chm.cpp
index 1a58175c2d..f89fbe535e 100644
--- a/src/html/chm.cpp
+++ b/src/html/chm.cpp
@@ -696,7 +696,7 @@ wxChmInputStream::CreateHHPStream()
 bool wxChmInputStream::CreateFileStream(const wxString& pattern)
 {
     wxFileInputStream * fin;
-    wxString tmpfile = wxFileName::CreateTempFileName(_T("chmstrm"), NULL);
+    wxString tmpfile = wxFileName::CreateTempFileName(_T("chmstrm"));
 
     if ( tmpfile.empty() )
     {