diff --git a/dune/tectonic/nicefunction.hh b/dune/tectonic/nicefunction.hh
index 027e6052922c366c2371891e44ad1d141ae45e3f..81625152d6426a2e666be05d7c8fd6f731818e46 100644
--- a/dune/tectonic/nicefunction.hh
+++ b/dune/tectonic/nicefunction.hh
@@ -55,14 +55,14 @@ class RuinaFunction : public NiceFunction {
     if (eta * s <= rho)
       return 0;
 
-    return normalStress * (a * std::log(s) + mu);
+    return coefficient * normalStress * (a * std::log(s) + mu);
   }
 
   double virtual rightDifferential(double s) const {
     if (eta * s <= rho)
       return 0;
 
-    return normalStress * (a * std::log(s) + mu);
+    return coefficient * normalStress * (a * std::log(s) + mu);
   }
 
 private: