diff --git a/Minkowski_sum_2/include/CGAL/Minkowski_sum_2/Minkowski_sum_conv_2.h b/Minkowski_sum_2/include/CGAL/Minkowski_sum_2/Minkowski_sum_conv_2.h
index 1383240a617..6780f5cca98 100644
--- a/Minkowski_sum_2/include/CGAL/Minkowski_sum_2/Minkowski_sum_conv_2.h
+++ b/Minkowski_sum_2/include/CGAL/Minkowski_sum_2/Minkowski_sum_conv_2.h
@@ -173,7 +173,7 @@ public:
     CGAL_precondition (pgn2.is_simple());
 
     // Prepare the vector of directions for the first polygon.
-    const unsigned int    n1 = pgn1.size();
+    const unsigned int    n1 = static_cast<unsigned int>(pgn1.size());
     const bool            forward1 = (pgn1.orientation() == COUNTERCLOCKWISE);
     std::vector<Direction_2>  dirs1 (n1);
     Vertex_circulator         curr1, next1;
@@ -193,7 +193,7 @@ public:
 
     // Prepare the vector of directions for the second polygon.
     // Also prepare a list containing all reflex vertices of this polygon.
-    const unsigned int    n2 = pgn2.size();
+    const unsigned int    n2 = static_cast<unsigned int>(pgn2.size());
     const bool            forward2 = (pgn2.orientation() == COUNTERCLOCKWISE);
     std::vector<Direction_2>  dirs2 (n2);
     Vertex_circulator         prev2, curr2, next2;
@@ -527,7 +527,7 @@ private:
     // the list contains no "cyclic" sub-cylces. We do that by making sure that
     // the first and last segments of the list correspond to traversals of
     // different polygons.
-    int     steps = cycle.size();
+    int     steps = static_cast<int>(cycle.size());
 
     while (steps > 0 &&
            cycle.front().label().get_flag() == 
diff --git a/Minkowski_sum_2/include/CGAL/Small_side_angle_bisector_decomposition_2.h b/Minkowski_sum_2/include/CGAL/Small_side_angle_bisector_decomposition_2.h
index 2feca19f2fa..56d8cb4a35a 100644
--- a/Minkowski_sum_2/include/CGAL/Small_side_angle_bisector_decomposition_2.h
+++ b/Minkowski_sum_2/include/CGAL/Small_side_angle_bisector_decomposition_2.h
@@ -247,7 +247,7 @@ private:
                                  unsigned int i) const
   {
     if (i == 0)
-      return (vec.size() - 1);
+      return static_cast<unsigned int>(vec.size() - 1);
     return (i - 1);
   }
 
@@ -414,7 +414,7 @@ private:
                                 Point_vector_2& vec) const
   {
     // Resize the vector to fit the polygon.
-    const unsigned int  n = pgn.size();
+    const unsigned int  n = static_cast<unsigned int>(pgn.size());
     const bool          forward = (pgn.orientation() == COUNTERCLOCKWISE);
     Vertex_circulator          prev, curr, next;
     unsigned int        reflex_count = 0;
@@ -755,7 +755,7 @@ private:
           }
           else if (*iter < ind1)
           {
-            vec2[i2].visible.push_back (*iter + vec.size() - ind2);
+            vec2[i2].visible.push_back (*iter + static_cast<unsigned int>(vec.size()) - ind2);
           }
         }
         
@@ -769,7 +769,7 @@ private:
           }
           else if (*iter < ind1)
           {
-            vec2[i2].non_visible.push_back (*iter + vec.size() - ind2);
+            vec2[i2].non_visible.push_back (*iter + static_cast<int>(vec.size()) - ind2);
           }
         }
       }
@@ -922,7 +922,7 @@ private:
   OutputIterator _output_polygon (const Point_vector_2& vec,
                                   OutputIterator oi) const
   {
-    const unsigned int    n = vec.size();
+    const unsigned int    n = static_cast<int>(vec.size());
     Polygon_2             pgn;
     unsigned int          k;