diff --git a/include/laser/landmark/landmark_polyline_2D.h b/include/laser/landmark/landmark_polyline_2D.h
index cac3d358ef5e5b33cb6d35eaa6def2088a03374b..8d8ce4b3e10c456cec2a8e02a6c74fab18c97570 100644
--- a/include/laser/landmark/landmark_polyline_2D.h
+++ b/include/laser/landmark/landmark_polyline_2D.h
@@ -200,7 +200,7 @@ class LandmarkPolyline2D : public LandmarkBase
 
         /** \brief Adds all stateBlocks of the frame to the wolfProblem list of new stateBlocks
          **/
-        virtual void registerNewStateBlocks();
+        virtual void registerNewStateBlocks() const;
         virtual void removeStateBlocks();
 
         /** Factory method to create new landmarks from YAML nodes
diff --git a/src/landmark/landmark_polyline_2D.cpp b/src/landmark/landmark_polyline_2D.cpp
index 2ca2a31504e267980019b5f704b052cb019a1f17..7b1edfbed54edd5b1b708c0517560b0417540c45 100644
--- a/src/landmark/landmark_polyline_2D.cpp
+++ b/src/landmark/landmark_polyline_2D.cpp
@@ -907,7 +907,7 @@ void LandmarkPolyline2D::mergeLandmark(const LandmarkPolyline2DPtr _merged_lmk,
     //std::cout << "\tLandmark deleted\n";
 }
 
-void LandmarkPolyline2D::registerNewStateBlocks()
+void LandmarkPolyline2D::registerNewStateBlocks() const
 {
     LandmarkBase::registerNewStateBlocks();
 	if (getProblem())