diff --git a/dune/tectonic/myconvexproblem.hh b/dune/tectonic/myconvexproblem.hh
index 76542cd4b1f2875d06ab7de2796271827f8cf25c..19ea2f523d9e26f417189fdc0d4dc0a1a7fc03a2 100644
--- a/dune/tectonic/myconvexproblem.hh
+++ b/dune/tectonic/myconvexproblem.hh
@@ -1,5 +1,7 @@
 // Based on dune/tnnmg/problem-classes/convexproblem.hh
 // Allows phi to be const; does away with everything we do not need
+// convexproblem.hh also currently uses *(NULL) which leads to undefined
+// behaviour
 
 #ifndef MY_CONVEX_PROBLEM_HH
 #define MY_CONVEX_PROBLEM_HH