diff --git a/Surface_mesh/include/CGAL/Surface_mesh/Properties.h b/Surface_mesh/include/CGAL/Surface_mesh/Properties.h
index 651b0241da7..efdd4586966 100644
--- a/Surface_mesh/include/CGAL/Surface_mesh/Properties.h
+++ b/Surface_mesh/include/CGAL/Surface_mesh/Properties.h
@@ -395,7 +395,7 @@ public:
     typename Get_pmap_type<T>::type
     get_or_add(const std::string& name, const T t=T())
     {
-      std::optional<Get_pmap_type<T>::type> out = get<T>(name);
+      std::optional<typename Get_pmap_type<T>::type> out = get<T>(name);
       if (out.has_value())
         return out.value();
       else