diff --git a/BGL/include/CGAL/boost/graph/properties_OpenMesh.h b/BGL/include/CGAL/boost/graph/properties_OpenMesh.h
index 7f1d44979d1..5b252c00ee1 100644
--- a/BGL/include/CGAL/boost/graph/properties_OpenMesh.h
+++ b/BGL/include/CGAL/boost/graph/properties_OpenMesh.h
@@ -202,7 +202,7 @@ public:
     : sm_(pm.sm_)
     {}
 
-  reference operator[](key_type v)
+  reference operator[](key_type v) const
   {
 #if defined(CGAL_USE_OM_POINTS)
     return sm_->point(v);