diff --git a/Classification/include/CGAL/Classification/Mesh_feature_generator.h b/Classification/include/CGAL/Classification/Mesh_feature_generator.h
index 935abc76a1e..6892f3c6b02 100644
--- a/Classification/include/CGAL/Classification/Mesh_feature_generator.h
+++ b/Classification/include/CGAL/Classification/Mesh_feature_generator.h
@@ -65,15 +65,20 @@ namespace Classification {
   \brief Generates a set of generic features for surface mesh
   classification.
 
-  This class takes care of computing all necessary data structures and
-  of generating a set of generic features at multiple scales to
-  increase the reliability of the classification.
+  This class takes care of computing and storing all necessary data
+  structures and of generating a set of generic features at multiple
+  scales to increase the reliability of the classification.
 
   A `PointMap` is required: this map should associate each face of the
   mesh to a representative point (for example, the center of mass of
   the face). It is used to generate point set features by considering
   the mesh as a point set.
 
+  \warning The generated features use data structures that are stored
+  inside the generator. For this reason, the generator should be
+  instantiated _within the same scope_ as the feature set and should
+  not be deleted before the feature set.
+
   \tparam GeomTraits model of \cgal Kernel.
   \tparam FaceListGraph model of `FaceListGraph`. 
   \tparam PointMap model of `ReadablePropertyMap` whose key type is
diff --git a/Classification/include/CGAL/Classification/Point_set_feature_generator.h b/Classification/include/CGAL/Classification/Point_set_feature_generator.h
index 2e10f364e0f..adaf9eb5782 100644
--- a/Classification/include/CGAL/Classification/Point_set_feature_generator.h
+++ b/Classification/include/CGAL/Classification/Point_set_feature_generator.h
@@ -67,9 +67,14 @@ namespace Classification {
   \brief Generates a set of generic features for point set
   classification.
 
-  This class takes care of computing all necessary data structures and
-  of generating a set of generic features at multiple scales to
-  increase the reliability of the classification.
+  This class takes care of computing and storing all necessary data
+  structures and of generating a set of generic features at multiple
+  scales to increase the reliability of the classification.
+
+  \warning The generated features use data structures that are stored
+  inside the generator. For this reason, the generator should be
+  instantiated _within the same scope_ as the feature set and should
+  not be deleted before the feature set.
 
   \tparam GeomTraits model of \cgal Kernel.
   \tparam PointRange model of `ConstRange`. Its iterator type is