diff --git a/include/core/processor/track_matrix.h b/include/core/processor/track_matrix.h
index 883ed5b264d414ecda904cbd3f0f094d44dd1382..8fb9538d3fa4e85465f23248a34aca9acc2276d8 100644
--- a/include/core/processor/track_matrix.h
+++ b/include/core/processor/track_matrix.h
@@ -125,8 +125,10 @@ class TrackMatrix
 //        bool            markKeyframe(CaptureBasePtr _capture);
 //        bool            unmarkKeyframe(CaptureBasePtr _capture);
 
-        const map<SizeStd, Track>& getTracks(){return tracks_;}
-        const map<CaptureBasePtr, Snapshot >& getSnapshots(){return snapshots_;}
+        const map<SizeStd, Track>& getTracks() {return tracks_;}
+        const map<SizeStd, Track>& getTracks() const {return tracks_;}
+        const map<CaptureBasePtr, Snapshot >& getSnapshots() {return snapshots_;}
+        const map<CaptureBasePtr, Snapshot >& getSnapshots() const {return snapshots_;}
 
     private: