diff --git a/Number_types/include/CGAL/Quotient.h b/Number_types/include/CGAL/Quotient.h
index de1e6adbebe..c27dc82af73 100644
--- a/Number_types/include/CGAL/Quotient.h
+++ b/Number_types/include/CGAL/Quotient.h
@@ -33,6 +33,9 @@
 #include <CGAL/Kernel/mpl.h>
 
 #include <boost/operators.hpp>
+#ifdef CGAL_USE_BOOST_MP
+#include <boost/multiprecision/cpp_int.hpp>
+#endif // CGAL_USE_BOOST_MP
 
 namespace CGAL {
 
@@ -46,6 +49,15 @@ template < typename NT >
 inline void
 simplify_quotient(NT &, NT &) {}
 
+#ifdef CGAL_USE_BOOST_MP
+inline void
+simplify_quotient(boost::multiprecision::cpp_int & a, boost::multiprecision::cpp_int & b) {
+  const boost::multiprecision::cpp_int r = boost::multiprecision::gcd(a, b);
+  a /= r;
+  b /= r;
+}
+#endif // CGAL_USE_BOOST_MP
+
 // This one should be replaced by some functor or tag.
 // Meanwhile, the class is specialized for Gmpz, mpz_class, leda_integer.
 template < typename NT >
diff --git a/Number_types/include/CGAL/boost_mp.h b/Number_types/include/CGAL/boost_mp.h
index d64cdf650ae..c650273aa9f 100644
--- a/Number_types/include/CGAL/boost_mp.h
+++ b/Number_types/include/CGAL/boost_mp.h
@@ -794,14 +794,6 @@ namespace internal {
 
 #ifdef CGAL_USE_BOOST_MP
 
-template < >
-inline void
-simplify_quotient(boost::multiprecision::cpp_int & a, boost::multiprecision::cpp_int & b) {
-  const boost::multiprecision::cpp_int r = boost::multiprecision::gcd(a, b);
-  a /= r;
-  b /= r;
-}
-
 template< > class Real_embeddable_traits< Quotient<boost::multiprecision::cpp_int> >
     : public INTERN_QUOTIENT::Real_embeddable_traits_quotient_base< Quotient<boost::multiprecision::cpp_int> > {