diff --git a/dune/solvers/iterationsteps/cgstep.hh b/dune/solvers/iterationsteps/cgstep.hh
index 12e9dbb74c0e624969ed430d7e0821091f74b329..f5bac9aef7f77151b0aadfc51701e5a4de1b8aa7 100644
--- a/dune/solvers/iterationsteps/cgstep.hh
+++ b/dune/solvers/iterationsteps/cgstep.hh
@@ -13,6 +13,7 @@ namespace Dune {
         {
         public:
             CGStep()
+                : preconditioner_(nullptr)
             {}
 
             CGStep(const MatrixType& matrix,