diff --git a/include/core/processor/is_motion.h b/include/core/processor/is_motion.h
index 08e500822a6fcdabcafc63d150c701d0c7d51e9b..6fd65feecee502218688a7943df502cc5c0e4077 100644
--- a/include/core/processor/is_motion.h
+++ b/include/core/processor/is_motion.h
@@ -34,7 +34,7 @@ class IsMotion
         void addToProblem(ProblemPtr _prb_ptr, IsMotionPtr _motion_ptr);
    
     protected:
-        std::string state_structure_; ///< The structure of the state vector (to retrieve state blocks from frames)
+        StateStructure state_structure_; ///< The structure of the state vector (to retrieve state blocks from frames)
 
 };