diff --git a/Cartesian_kernel/include/CGAL/Cartesian_converter.h b/Cartesian_kernel/include/CGAL/Cartesian_converter.h
index d87dcac6610..cf88966fd41 100644
--- a/Cartesian_kernel/include/CGAL/Cartesian_converter.h
+++ b/Cartesian_kernel/include/CGAL/Cartesian_converter.h
@@ -96,14 +96,14 @@ public:
 
     using Base::operator();
 
-    const Origin&
-    operator()(const Origin& o) const
+    Origin
+    operator()(Origin o) const
     {
         return o;
     }
 
-    const Null_vector&
-    operator()(const Null_vector& n) const
+    Null_vector
+    operator()(Null_vector n) const
     {
         return n;
     }
diff --git a/Homogeneous_kernel/include/CGAL/Homogeneous_converter.h b/Homogeneous_kernel/include/CGAL/Homogeneous_converter.h
index 9f04f090b4a..14ca6c059c3 100644
--- a/Homogeneous_kernel/include/CGAL/Homogeneous_converter.h
+++ b/Homogeneous_kernel/include/CGAL/Homogeneous_converter.h
@@ -50,14 +50,14 @@ public:
 
     using Base::operator();
 
-    const Origin&
-    operator()(const Origin& o) const
+    Origin
+    operator()(Origin o) const
     {
         return o;
     }
 
-    const Null_vector&
-    operator()(const Null_vector& n) const
+    Null_vector
+    operator()(Null_vector n) const
     {
         return n;
     }