diff --git a/src/DGtal/geometry/tools/MelkmanConvexHull.h b/src/DGtal/geometry/tools/MelkmanConvexHull.h
index ac2028e2a4..f6ac1eef97 100644
--- a/src/DGtal/geometry/tools/MelkmanConvexHull.h
+++ b/src/DGtal/geometry/tools/MelkmanConvexHull.h
@@ -147,13 +147,13 @@ namespace DGtal
      * Rationale: we do not want to iterate over the same point, 
      * duplicated at the begin and at the end of the container.  
      */
-    ConstIterator begin();
+    ConstIterator begin() const;
 
     /**
      * End iterator 
      * @return a const iterator to the end of the container
      */
-    ConstIterator end();
+    ConstIterator end() const;
 
     /**
      * Writes/Displays the object on an output stream.
diff --git a/src/DGtal/geometry/tools/MelkmanConvexHull.ih b/src/DGtal/geometry/tools/MelkmanConvexHull.ih
index 41893e0beb..1b1583cb3d 100644
--- a/src/DGtal/geometry/tools/MelkmanConvexHull.ih
+++ b/src/DGtal/geometry/tools/MelkmanConvexHull.ih
@@ -109,7 +109,7 @@ DGtal::MelkmanConvexHull<TPoint, TOrientationFunctor>::add(const Point& aPoint)
 template <typename TPoint, typename TOrientationFunctor>
 inline
 typename DGtal::MelkmanConvexHull<TPoint, TOrientationFunctor>::ConstIterator
-DGtal::MelkmanConvexHull<TPoint, TOrientationFunctor>::begin()
+DGtal::MelkmanConvexHull<TPoint, TOrientationFunctor>::begin() const
 {
   if (myContainer.size() == 0)
     return myContainer.end(); 
@@ -121,7 +121,7 @@ DGtal::MelkmanConvexHull<TPoint, TOrientationFunctor>::begin()
 template <typename TPoint, typename TOrientationFunctor>
 inline
 typename DGtal::MelkmanConvexHull<TPoint, TOrientationFunctor>::ConstIterator
-DGtal::MelkmanConvexHull<TPoint, TOrientationFunctor>::end()
+DGtal::MelkmanConvexHull<TPoint, TOrientationFunctor>::end() const
 {
   return myContainer.end(); 
 }