diff --git a/dlls/hhctrl.ocx/help.c b/dlls/hhctrl.ocx/help.c
index a19e1e6..092e97e 100644
--- a/dlls/hhctrl.ocx/help.c
+++ b/dlls/hhctrl.ocx/help.c
@@ -129,7 +129,7 @@
         return FALSE;
     }
 
-    wsprintfW(buf, url_format, full_path, index[0] == '/' ? empty : slash, index);
+    wsprintfW(buf, url_format, full_path, (!index || index[0] == '/') ? empty : slash, index);
 
     /* FIXME: HACK */
     if((ptr = strchrW(buf, '#')))