diff --git a/Operations_on_polyhedra/include/CGAL/orient_polygon_soup.h b/Operations_on_polyhedra/include/CGAL/orient_polygon_soup.h
index b36fcf58e85..6804e5ae5e7 100644
--- a/Operations_on_polyhedra/include/CGAL/orient_polygon_soup.h
+++ b/Operations_on_polyhedra/include/CGAL/orient_polygon_soup.h
@@ -171,7 +171,7 @@ public:
                 const std::size_t& i0 = polygons[index][j];
                 const std::size_t& i1 = polygons[index][ j+1 < size ? j+1: 0];
                 CGAL_assertion_code(const bool r = )
-                  edges[std::make_pair(i0, i1)].erase(index);
+                  edges[std::make_pair(i0, i1)].erase(index) != 0;
                 CGAL_assertion(r);
               }
               inverse_orientation(index);