diff --git a/src/pe/ccd/HashGrids.h b/src/pe/ccd/HashGrids.h
index 73400309b7ef8363dd6f41c7513176576a381dc9..04604890dd5192ad914d2d554948b91ad50a11d3 100644
--- a/src/pe/ccd/HashGrids.h
+++ b/src/pe/ccd/HashGrids.h
@@ -289,7 +289,7 @@ public:
    //@}
    //**********************************************************************************************
 
-   void    update(WcTimingTree* tt);
+   void    update(WcTimingTree* tt = NULL);
    //**Implementation of ICCD interface ********************************************************
    virtual PossibleContacts& generatePossibleContacts( WcTimingTree* tt = NULL );