diff --git a/CHANGELOG.md b/CHANGELOG.md
index 09e9246d0623cba781c1f0f9470de328ee7809c2..a6907a3b8b293089ac8d66184cd8ad7517b44a47 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,10 @@ Differences Between DuMuX 2.9 and DuMuX 2.10
     - multidomain should now work with all compilers (optimzed) without segfaults
 
 * IMMEDIATE INTERFACE CHANGES not allowing/requiring a deprecation period:
+    - The problem class interface needs to provide the method maxTimeStepSize().
+      This is important if you implement problem classes not deriving from the base
+      problem classes in Dumux (ImplicitProblem, OneModelProblem,
+      ImpetProblem, and MultidomainProblem).
 
 * Deprecated PROPERTY and PARAMETER NAMES, to be removed after 2.10: BEWARE: The
   compiler will not print any warning if a deprecated property or parameter name