diff --git a/dune/tectonic/myblockproblem.hh b/dune/tectonic/myblockproblem.hh
index 08cce02bd991859ec644a060eac50bf4f559e0fa..1910eadefeec953663e62be7ae83b075dca64af5 100644
--- a/dune/tectonic/myblockproblem.hh
+++ b/dune/tectonic/myblockproblem.hh
@@ -132,7 +132,7 @@ template <class MyConvexProblemTypeTEMPLATE> class MyBlockProblem {
     psi.subDiff(0, D);
     if (D[1] > 0) {
       // NOTE: Numerical instability can actually get us here
-      assert(std::abs(D[1]) < 1e-13);
+      assert(std::abs(D[1]) < 1e-12);
       return 0;
     }