diff --git a/dune/tectonic/myblockproblem.hh b/dune/tectonic/myblockproblem.hh
index e3fae3fffc6783eee4eaf1e260c6749c4850a8ba..08cce02bd991859ec644a060eac50bf4f559e0fa 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-15);
+      assert(std::abs(D[1]) < 1e-13);
       return 0;
     }