diff --git a/dune/dorie/solver/param_van_genuchten.hh b/dune/dorie/solver/param_van_genuchten.hh
index 6785397e97012032227d3096b67e7a67d0e28d4a..f12185de01cb9c89d898ea4138e93de036640df3 100644
--- a/dune/dorie/solver/param_van_genuchten.hh
+++ b/dune/dorie/solver/param_van_genuchten.hh
@@ -22,8 +22,8 @@ namespace Dune {
       explicit MualemVanGenuchten(const ParameterTree& fieldConfig_, const Dune::MPIHelper& helper_,
         Interpolator& interpolator_, H5File& h5file_, const int verbose_)
       : PB(fieldConfig_, "vanGenuchten", parameterArray, helper_, interpolator_, h5file_, verbose_)
-      , thetaR("theta_r", 0.0, 1.0), thetaS("theta_s", 0.0, 1.0), alpha("alpha", -10.0, 0.0)
-      , n("n", 1.0, 100.0), tau("tau", -100.0, 0.0), k0("k0", 0.0, 1.0)
+      , thetaR("theta_r", 0.0, 1.0), thetaS("theta_s", 0.0, 1.0), alpha("alpha", -20.0, 0.0)
+      , n("n", 1.0, 100.0), tau("tau", -100.0, 1.0), k0("k0", 0.0, 1.0)
       {
         parameterArray.push_back(& thetaR);
         parameterArray.push_back(& thetaS);