diff --git a/test/testinst/GTestInstDir.hpp b/test/testinst/GTestInstDir.hpp
index 3e19acc..96d2763 100644
--- a/test/testinst/GTestInstDir.hpp
+++ b/test/testinst/GTestInstDir.hpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *     GTestInstDir.hpp  -  Test instrument direction class                *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2012-2014 by Jean-Baptiste Cayrou                        *
+ *  copyright (C) 2012-2020 by Jean-Baptiste Cayrou                        *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -86,7 +86,8 @@ public:
     
     GTestInstDir* clone(void) const{ return new GTestInstDir(*this); }
     std::string   classname(void) const { return "GTestInstDir"; }
-        
+    double        hash(void) const { return 41.0; };
+    
     std::string  print(const GChatter& chatter = NORMAL) const{ 
         std::string result = "=== GTestInstDir ===";
             return result;