diff --git a/Triangulation_2/doc/Triangulation_2/Concepts/ConstrainedTriangulationTraits_2.h b/Triangulation_2/doc/Triangulation_2/Concepts/ConstrainedTriangulationTraits_2.h
index e13c8388506..dd235e31e37 100644
--- a/Triangulation_2/doc/Triangulation_2/Concepts/ConstrainedTriangulationTraits_2.h
+++ b/Triangulation_2/doc/Triangulation_2/Concepts/ConstrainedTriangulationTraits_2.h
@@ -80,7 +80,8 @@ typedef unspecified_type Compute_squared_distance_2;
 A function object whose
 `operator()` computes the bounding box of a point.
 
-`Point_2 operator()(Point_2 p);` Returns the bounding box of `p`. 
+`unspecified_type operator()(Point_2 p);` Returns the bounding box of `p`.
+The result type is either `Bbox_2` or `Bbox_3` (for projection traits classes).
 */ 
 typedef unspecified_type Compute_bounding_box_2;