diff --git a/dune/solvers/operators/nulloperator.hh b/dune/solvers/operators/nulloperator.hh
index cff406947d5301b4ef7354c51981f3a28c9d679a..9816f3b2534a093214d027342bedf50846422af3 100644
--- a/dune/solvers/operators/nulloperator.hh
+++ b/dune/solvers/operators/nulloperator.hh
@@ -89,6 +89,17 @@ class NullOperator
         void operator*=(const field_type&)
         {}
 
+        size_type M() const
+        {
+            return 0;
+        }
+
+        size_type N() const
+        {
+            return 0;
+        }
+
+
 };
 
 #endif