diff --git a/Stream_support/include/CGAL/IO/OFF.h b/Stream_support/include/CGAL/IO/OFF.h
index bfbac4612e3..5013a9bdf71 100644
--- a/Stream_support/include/CGAL/IO/OFF.h
+++ b/Stream_support/include/CGAL/IO/OFF.h
@@ -14,6 +14,7 @@
 #include <CGAL/IO/OFF/Scanner_OFF.h>
 #include <CGAL/IO/OFF/File_scanner_OFF.h>
 #include <CGAL/IO/OFF/File_writer_OFF.h>
+#include <CGAL/IO/OFF/generic_copy_OFF.h>
 #include <CGAL/IO/helpers.h>
 #include <CGAL/IO/Generic_writer.h>
 
diff --git a/Stream_support/include/CGAL/IO/OFF/Scanner_OFF.h b/Stream_support/include/CGAL/IO/OFF/Scanner_OFF.h
index a7a9617b850..b6cd67707bb 100644
--- a/Stream_support/include/CGAL/IO/OFF/Scanner_OFF.h
+++ b/Stream_support/include/CGAL/IO/OFF/Scanner_OFF.h
@@ -59,7 +59,7 @@ public:
     typedef File_scanner_OFF                   Scanner;
     typedef I_Scanner_OFF_vertex_iterator<Pt>  Self;
 
-  I_Scanner_OFF_vertex_iterator(std::size_t cnt) : m_scan(0), m_cnt(cnt+1) {}
+  I_Scanner_OFF_vertex_iterator(std::size_t cnt) : m_scan(nullptr), m_cnt(cnt+1) {}
     I_Scanner_OFF_vertex_iterator( Scanner& s, int cnt)
         : m_scan(&s), m_cnt(cnt)
     {
@@ -118,7 +118,7 @@ private:
 public:
 
     I_Scanner_OFF_vertex_and_normals_iterator( int cnt)
-        : m_scan(0), m_cnt(cnt+1) {}
+        : m_scan(nullptr), m_cnt(cnt+1) {}
     I_Scanner_OFF_vertex_and_normals_iterator( Scanner& s, int cnt)
         : m_scan(&s), m_cnt(cnt)
     {
@@ -184,7 +184,7 @@ public:
     typedef I_Scanner_OFF_facet_iterator  Self;
     typedef value_type::iterator          iterator;
 
-  I_Scanner_OFF_facet_iterator( std::size_t cnt) : m_scan(0), m_cnt(cnt+1) {}
+  I_Scanner_OFF_facet_iterator( std::size_t cnt) : m_scan(nullptr), m_cnt(cnt+1) {}
   I_Scanner_OFF_facet_iterator( Scanner& s, std::size_t cnt)
         : m_scan(&s), m_cnt(cnt)
     {
diff --git a/Stream_support/include/CGAL/IO/OFF/generic_copy_OFF.h b/Stream_support/include/CGAL/IO/OFF/generic_copy_OFF.h
index ba264567d68..eb19da8b328 100644
--- a/Stream_support/include/CGAL/IO/OFF/generic_copy_OFF.h
+++ b/Stream_support/include/CGAL/IO/OFF/generic_copy_OFF.h
@@ -52,7 +52,7 @@ generic_copy_OFF(File_scanner_OFF& scanner,
   writer.write_header(out,
                       scanner.size_of_vertices(),
                       scanner.polyhedral_surface() ? scanner.size_of_halfedges() : 0,
-                       scanner.size_of_facets());
+                      scanner.size_of_facets());
 
   // read in all vertices
   double x, y, z; // Point coordinates.
diff --git a/Stream_support/include/CGAL/IO/OI/File_writer_inventor.h b/Stream_support/include/CGAL/IO/OI/File_writer_inventor.h
index a3fe97d865c..119f0e5b71b 100644
--- a/Stream_support/include/CGAL/IO/OI/File_writer_inventor.h
+++ b/Stream_support/include/CGAL/IO/OI/File_writer_inventor.h
@@ -25,19 +25,19 @@ namespace CGAL {
 
 class File_writer_inventor
 {
-  Inventor_ostream_base* m_os;
+  Inventor_ostream_base m_os;
   std::size_t m_facets;
 
 public:
   File_writer_inventor() {}
-  std::ostream& out() const { return m_os->os(); }
+  std::ostream& out() const { return m_os.os(); }
 
-  void write_header(Inventor_ostream_base& o,
+  void write_header(std::ostream& o,
                     std::size_t vertices,
                     std::size_t halfedges,
                     std::size_t facets)
   {
-    m_os = &o;
+    m_os.open(o);
     m_facets = facets;
 
     out() << "# " << vertices << " vertices\n";
diff --git a/Stream_support/include/CGAL/IO/OI/Inventor_ostream.h b/Stream_support/include/CGAL/IO/OI/Inventor_ostream.h
index 975ea1ed542..088458d11a8 100644
--- a/Stream_support/include/CGAL/IO/OI/Inventor_ostream.h
+++ b/Stream_support/include/CGAL/IO/OI/Inventor_ostream.h
@@ -31,10 +31,10 @@ namespace CGAL {
 class Inventor_ostream_base
 {
 private:
-  std::ostream* m_os;
+  std::ostream* m_os = nullptr;
 
 public:
-  Inventor_ostream_base() : m_os(0)  {}
+  Inventor_ostream_base() : m_os(nullptr)  {}
   Inventor_ostream_base(std::ostream& o) : m_os(&o) {}
   ~Inventor_ostream_base() { close(); }
   void open(std::ostream& o) { m_os = &o; }
@@ -53,13 +53,13 @@ public:
     return m_os && !m_os->fail();
   }
 
-  std::ostream& os()
+  std::ostream& os() const
   {
-    // The behaviour if m_os == 0 could be changed to return
+    // The behaviour if m_os == nullptr could be changed to return
     // cerr or a file handle to /dev/null. The latter one would
     // mimick the behaviour that one can still use a stream with
     // an invalid stream, but without producing any output.
-    CGAL_assertion( m_os != 0 );
+    CGAL_assertion( m_os != nullptr );
     return *m_os;
   }
 };
diff --git a/Stream_support/include/CGAL/IO/VRML/File_writer_VRML_2.h b/Stream_support/include/CGAL/IO/VRML/File_writer_VRML_2.h
index eabebd32eb9..bb637b85888 100644
--- a/Stream_support/include/CGAL/IO/VRML/File_writer_VRML_2.h
+++ b/Stream_support/include/CGAL/IO/VRML/File_writer_VRML_2.h
@@ -21,26 +21,27 @@
 
 #include <CGAL/IO/VRML/VRML_2_ostream.h>
 
-#include <iostream>
 #include <cstddef>
+#include <iostream>
 
 namespace CGAL {
 
 class File_writer_VRML_2
 {
-  VRML_2_ostream* m_os;
+  VRML_2_ostream m_os;
   std::size_t m_facets;
 
 public:
   File_writer_VRML_2() {}
-  std::ostream& out() const { return m_os->os(); }
 
-  void write_header(VRML_2_ostream& o,
+  std::ostream& out() const { return m_os.os(); }
+
+  void write_header(std::ostream& o,
                     std::size_t vertices,
                     std::size_t halfedges,
                     std::size_t facets)
   {
-    m_os = &o;
+    m_os.open(o);
     m_facets = facets;
 
     out() << "        #-- Begin of Polygon Mesh\n";
@@ -80,7 +81,7 @@ public:
              "                        coordIndex  [" << std::endl;
   }
 
-  void write_facet_begin( std::size_t) { out() << "                            "; }
+  void write_facet_begin(std::size_t) { out() << "                            "; }
   void write_facet_vertex_index( std::size_t idx) { out() << idx << ',';}
   void write_facet_end() { out() << "-1,\n"; }
 };
diff --git a/Stream_support/include/CGAL/IO/VRML/VRML_2_ostream.h b/Stream_support/include/CGAL/IO/VRML/VRML_2_ostream.h
index d5d3a36a37f..0f38ebebc40 100644
--- a/Stream_support/include/CGAL/IO/VRML/VRML_2_ostream.h
+++ b/Stream_support/include/CGAL/IO/VRML/VRML_2_ostream.h
@@ -27,7 +27,7 @@ namespace CGAL {
 class VRML_2_ostream
 {
 public:
-  VRML_2_ostream() : m_os(0) {}
+  VRML_2_ostream() : m_os(nullptr) {}
   VRML_2_ostream(std::ostream& o) : m_os(&o) { header(); }
   ~VRML_2_ostream() { close(); }
 
@@ -44,13 +44,13 @@ public:
 
   explicit operator bool () { return m_os && !m_os->fail(); }
 
-  std::ostream& os()
+  std::ostream& os() const
   {
-    // The behaviour if m_os == 0 could be changed to return
+    // The behaviour if m_os == nullptr could be changed to return
     // cerr or a file handle to /dev/null. The latter one would
     // mimick the behaviour that one can still use a stream with
     // an invalid stream, but without producing any output.
-    CGAL_assertion( m_os != 0 );
+    CGAL_assertion( m_os != nullptr );
     return *m_os;
   }