diff --git a/Number_types/test/Number_types/checked_NT.h b/Number_types/test/Number_types/checked_NT.h
index fd00a2da0f3..6c66b24cce0 100644
--- a/Number_types/test/Number_types/checked_NT.h
+++ b/Number_types/test/Number_types/checked_NT.h
@@ -1,4 +1,9 @@
 #include <cassert>
+#include <iostream>
+#include <utility>
+#include <CGAL/functional.h>
+#include <CGAL/number_utils.h>
+#include <CGAL/enum.h>
 
 namespace CGAL {
 template <class NT1, class NT2>