diff --git a/Constrained_triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_3.h b/Constrained_triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_3.h
index f8dc9afa48f..fa3ab821ce4 100644
--- a/Constrained_triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_3.h
+++ b/Constrained_triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_3.h
@@ -912,6 +912,8 @@ public:
   /// @{
   /*!
    * \brief determines if a facet is constrained.
+   * \param f is a facet of the triangulation, of type
+   *        \link TriangulationDataStructure_3::Facet `Triangulation::Facet`, as defined by its triangulation data structure \endlink.
    */
   bool is_facet_constrained(typename Triangulation::Facet f) const {
     return cdt_impl.is_facet_constrained(f);