diff --git a/MaterialLib/FractureModels/MohrCoulomb.cpp b/MaterialLib/FractureModels/MohrCoulomb.cpp
index 54932246c4d6a1ff3db7a4a8d99e37e31a239566..2519cbc23d15c0ee806ced02e61ce2da148bc51b 100644
--- a/MaterialLib/FractureModels/MohrCoulomb.cpp
+++ b/MaterialLib/FractureModels/MohrCoulomb.cpp
@@ -102,10 +102,10 @@ void MohrCoulomb<DisplacementDim>::computeConstitutiveRelation(
     else
     {
         for (int i=0; i<index_ns; i++)
-            dFs_dS[i] = boost::math::sign(tau) / tau * sigma[i];
+            dFs_dS[i] = sigma[i] / std::abs(tau);
 
         for (int i=0; i<index_ns; i++)
-            dQs_dS[i] = boost::math::sign(tau) / tau * sigma[i];
+            dQs_dS[i] = sigma[i] / std::abs(tau);
     }
     dFs_dS[index_ns] = std::tan(mat.phi);
     dQs_dS[index_ns] = std::tan(mat.psi);