diff --git a/Polyhedron_IO/include/CGAL/IO/OFF_reader.h b/Polyhedron_IO/include/CGAL/IO/OFF_reader.h
index db5c46781e6..e7ce22456f7 100644
--- a/Polyhedron_IO/include/CGAL/IO/OFF_reader.h
+++ b/Polyhedron_IO/include/CGAL/IO/OFF_reader.h
@@ -14,12 +14,14 @@
 #include <CGAL/IO/File_scanner_OFF.h>
 #include <CGAL/IO/reader_helpers.h>
 
-#include <vector>
-#include <iostream>
 #include <CGAL/array.h>
 #include <CGAL/assertions.h>
+#include <CGAL/Container_helper.h>
 #include <CGAL/use.h>
 
+#include <vector>
+#include <iostream>
+
 namespace CGAL {
 
   template <class Point_3, class Polygon_3>
@@ -47,7 +49,7 @@ namespace CGAL {
       std::size_t no;
 
       scanner.scan_facet( no, i);
-      IO::internal::resize(polygons[i], no);
+      CGAL::internal::resize(polygons[i], no);
       for(std::size_t j = 0; j < no; ++j) {
         std::size_t id;
         scanner.scan_facet_vertex_index(id, i);
@@ -114,7 +116,7 @@ namespace CGAL {
       scanner.scan_facet( no, i);
       if(!in)
         return false;
-      IO::internal::resize(polygons[i], no);
+      CGAL::internal::resize(polygons[i], no);
       for(std::size_t j = 0; j < no; ++j) {
         std::size_t id;
         scanner.scan_facet_vertex_index(id, i);
diff --git a/Polyhedron_IO/include/CGAL/IO/STL_reader.h b/Polyhedron_IO/include/CGAL/IO/STL_reader.h
index 0899bc1ebf7..78925b113e8 100644
--- a/Polyhedron_IO/include/CGAL/IO/STL_reader.h
+++ b/Polyhedron_IO/include/CGAL/IO/STL_reader.h
@@ -15,6 +15,8 @@
 #include <CGAL/IO/io.h>
 #include <CGAL/IO/reader_helpers.h>
 
+#include <CGAL/Container_helper.h>
+
 #include <boost/cstdint.hpp> 
 
 #include <cctype>
@@ -43,7 +45,7 @@ bool read_ASCII_facet(std::istream& input,
   double x,y,z;
   Point p;
   Triangle ijk;
-  IO::internal::resize(ijk, 3);
+  CGAL::internal::resize(ijk, 3);
 
   while(input >> s)
   {
@@ -213,7 +215,7 @@ bool parse_binary_STL(std::istream& input,
     }
 
     Triangle ijk;
-    IO::internal::resize(ijk, 3);
+    CGAL::internal::resize(ijk, 3);
 
     for(int j=0; j<3; ++j)
     {