diff --git a/dune/tectonic/samplefunctional.hh b/dune/tectonic/samplefunctional.hh
index c6e0bc4e978e779b9009d24c16bd849585d720c7..1192ad6a4453f0743f3ff0f54b77cd20cbb0681a 100644
--- a/dune/tectonic/samplefunctional.hh
+++ b/dune/tectonic/samplefunctional.hh
@@ -26,9 +26,8 @@ template <int dim> class SampleFunctional {
       : A(A), b(b), phi(phi), ignore(ignore) {}
 
   double operator()(SmallVector const &v) const {
-    SmallVector y;
-    A.mv(v, y);               //      Av
-    y /= 2;                   //  1/2 Av
+    SmallVector y(0);
+    A.usmv(0.5, v, y);        //  1/2 Av
     y -= b;                   //  1/2 Av - b
     return y * v + (*phi)(v); // <1/2 Av - b,v> + H(|v|)
   }