diff --git a/Number_types/include/CGAL/Interval_nt.h b/Number_types/include/CGAL/Interval_nt.h
index 6fa983d6c7a..eb80c7b0c6f 100644
--- a/Number_types/include/CGAL/Interval_nt.h
+++ b/Number_types/include/CGAL/Interval_nt.h
@@ -1270,6 +1270,7 @@ namespace Eigen {
     typedef CGAL::Interval_nt<b> Real;
     typedef CGAL::Interval_nt<b> NonInteger;
     typedef CGAL::Interval_nt<b> Nested;
+    typedef double Literal;
 
     static inline Real epsilon() { return 0; }
     static inline Real dummy_precision() { return 0; }