diff --git a/Envelope_2/include/CGAL/Env_default_diagram_1.h b/Envelope_2/include/CGAL/Env_default_diagram_1.h
index c2143a821c1..2c0f016f2d9 100644
--- a/Envelope_2/include/CGAL/Env_default_diagram_1.h
+++ b/Envelope_2/include/CGAL/Env_default_diagram_1.h
@@ -41,7 +41,7 @@ public:
   typedef std::list<X_monotone_curve_2>             Curve_container;
   typedef typename Curve_container::iterator        Curve_iterator;
   typedef typename Curve_container::const_iterator  Curve_const_iterator;
-  typedef unsigned int                              Size;
+  typedef std::size_t                               Size;
 
   /*!
    * Representation of a diagram vertex, which stores the point it represents
diff --git a/Envelope_2/test/Envelope_2/test_envelope_segments.cpp b/Envelope_2/test/Envelope_2/test_envelope_segments.cpp
index 76daf8a5d96..6c03bb89aee 100644
--- a/Envelope_2/test/Envelope_2/test_envelope_segments.cpp
+++ b/Envelope_2/test/Envelope_2/test_envelope_segments.cpp
@@ -92,7 +92,7 @@ bool read_segments (const char *filename,
     }
       
     Segment_2 seg = Segment_2 (Point_2 (x1, y1), Point_2 (x2, y2));
-    segs.push_back (Curve_2(seg, segs.size()));
+    segs.push_back (Curve_2(seg, static_cast<int>(segs.size())));
   }
   ifile.close();