diff --git a/src/realtuple.hh b/src/realtuple.hh
index bd4dbab55146f321e5ea84c6ce399d65387f8b3c..8681b3c266deeba3343734a104e6f97d5d92bf8d 100644
--- a/src/realtuple.hh
+++ b/src/realtuple.hh
@@ -65,7 +65,7 @@ public:
         Dune::FieldMatrix<double,N,N> result;
         for (int i=0; i<N; i++)
             for (int j=0; j<N; j++)
-                result[i][j] = (i==j);
+                result[i][j] = 2*(i==j);
 
         return result;
     }