diff --git a/dumux/implicit/common/implicitpropertydefaults.hh b/dumux/implicit/common/implicitpropertydefaults.hh
index 5076a3c27e025d95e9fc6a4aa8c4d5c81c7471fe..ea67ef01429c988b4061445875cbf039da414617 100644
--- a/dumux/implicit/common/implicitpropertydefaults.hh
+++ b/dumux/implicit/common/implicitpropertydefaults.hh
@@ -39,6 +39,10 @@
 
 namespace Dumux {
 
+// forward declarations
+template <class TypeTag> class NewtonController;
+template <class TypeTag> class BoxBiCGStabILU0Solver;
+
 namespace Properties {
 //////////////////////////////////////////////////////////////////
 // Some defaults for very fundamental properties