diff --git a/Intersections_3/test/Intersections_3/bbox_other_do_intersect_test.cpp b/Intersections_3/test/Intersections_3/bbox_other_do_intersect_test.cpp
index 29debe09068..7737b0dadab 100644
--- a/Intersections_3/test/Intersections_3/bbox_other_do_intersect_test.cpp
+++ b/Intersections_3/test/Intersections_3/bbox_other_do_intersect_test.cpp
@@ -12,7 +12,7 @@
 //
 
 #include <string>
-
+#include <CGAL/Surface_mesh.h>
 #include <CGAL/config.h>
 
 #if defined(BOOST_MSVC)
diff --git a/Stream_support/include/CGAL/IO/helpers.h b/Stream_support/include/CGAL/IO/helpers.h
index 98830e089c8..ea376bff7b4 100644
--- a/Stream_support/include/CGAL/IO/helpers.h
+++ b/Stream_support/include/CGAL/IO/helpers.h
@@ -54,7 +54,10 @@ static inline std::string get_file_extension(const std::string fname)
     return std::string();
 
   std::string ext = fname.substr(dot+1, fname.length() - dot - 1);
-  std::transform(ext.begin(), ext.end(), ext.begin(), ::tolower);
+  std::transform(ext.begin(), ext.end(), ext.begin(),
+                 [](char c) {
+                   return static_cast<char>(std::tolower(static_cast<unsigned char>(c)));
+                 });
 
   return ext;
 }