diff --git a/Number_types/include/CGAL/GMP/Gmpq_type.h b/Number_types/include/CGAL/GMP/Gmpq_type.h
index 7c2aab99227..504ccc9e8c5 100644
--- a/Number_types/include/CGAL/GMP/Gmpq_type.h
+++ b/Number_types/include/CGAL/GMP/Gmpq_type.h
@@ -301,7 +301,7 @@ operator<<(std::ostream& os, const Gmpq &z)
 
 namespace Gmpq_detail {
   inline
-  bool is_space (const std::istream& is, std::istream::int_type c)
+  bool is_space (const std::istream& /*is*/, std::istream::int_type c)
   { 
     std::istream::char_type cc= c; 
     return 
@@ -315,13 +315,13 @@ namespace Gmpq_detail {
   }
 
   inline 
-  bool is_eof (const std::istream& is, std::istream::int_type c)
+  bool is_eof (const std::istream& /*is*/, std::istream::int_type c)
   {
     return c == std::istream::traits_type::eof();
   }
 
   inline
-  bool is_digit (const std::istream& is, std::istream::int_type c)
+  bool is_digit (const std::istream& /*is*/, std::istream::int_type c)
   {
     std::istream::char_type cc= c;
     return