diff --git a/Number_types/include/CGAL/Quotient_fwd.h b/Number_types/include/CGAL/Quotient_fwd.h
index aaa2a9bdab9..e04d5e9d56e 100644
--- a/Number_types/include/CGAL/Quotient_fwd.h
+++ b/Number_types/include/CGAL/Quotient_fwd.h
@@ -27,7 +27,7 @@
 CGAL_BEGIN_NAMESPACE
 
 template <class NT> class Quotient;
-template <class RT> class Root_of_traits;
+template <class RT> struct Root_of_traits;
 
 template <class NT>
 Quotient<NT> sqrt(const Quotient<NT> &);