diff --git a/Classification/include/CGAL/Classification/Label.h b/Classification/include/CGAL/Classification/Label.h
index 7b9e5b2a72f..7801942afcb 100644
--- a/Classification/include/CGAL/Classification/Label.h
+++ b/Classification/include/CGAL/Classification/Label.h
@@ -15,6 +15,7 @@
 #include <CGAL/license/Classification.h>
 #include <CGAL/IO/Color.h>
 
+#include <string>
 #include <memory>
 
 namespace CGAL {
diff --git a/Installation/include/CGAL/Mesh_3/Mesh_complex_3_in_triangulation_3_fwd.h b/Installation/include/CGAL/Mesh_3/Mesh_complex_3_in_triangulation_3_fwd.h
index d0202553abc..6d644faa1ec 100644
--- a/Installation/include/CGAL/Mesh_3/Mesh_complex_3_in_triangulation_3_fwd.h
+++ b/Installation/include/CGAL/Mesh_3/Mesh_complex_3_in_triangulation_3_fwd.h
@@ -13,6 +13,8 @@
 /// \file Mesh_complex_3_in_triangulation_3_fwd.h
 /// Forward declarations of the Mesh_3 package.
 
+#include <istream>
+
 #ifndef DOXYGEN_RUNNING
 namespace CGAL {