diff --git a/Nef_3/test/Nef_3/test_nef_3_io_EPEC.cpp b/Nef_3/test/Nef_3/test_nef_3_io_EPEC.cpp
index 03e0ff91ee5..ca62860f079 100644
--- a/Nef_3/test/Nef_3/test_nef_3_io_EPEC.cpp
+++ b/Nef_3/test/Nef_3/test_nef_3_io_EPEC.cpp
@@ -15,8 +15,11 @@ void test_write_read()
   typedef CGAL::Polyhedron_3< Kernel >     Polyhedron;
   typedef typename Kernel::Point_3         Point;
 
-  typename Kernel::RT n( std::string("6369051672525773"));
-  typename Kernel::RT d( std::string("4503599627370496"));
+  typename Kernel::RT n, d;
+  std::istringstream str_n("6369051672525773");
+  str_n >> n;
+  std::istringstream str_d("4503599627370496");
+  str_d >> d;
 
   Point p(n, 0, 0, d);
   Point q(0, n, 0, d);
diff --git a/Number_types/include/CGAL/mpq_class.h b/Number_types/include/CGAL/mpq_class.h
index bc653c8e955..6a0de04cf8f 100644
--- a/Number_types/include/CGAL/mpq_class.h
+++ b/Number_types/include/CGAL/mpq_class.h
@@ -273,6 +273,19 @@ public:
     }
 };
 
+// Copied from leda_rational.h
+namespace internal {
+  // See: Stream_support/include/CGAL/IO/io.h
+  template <typename ET>
+  void read_float_or_quotient(std::istream & is, ET& et);
+
+  template <>
+  inline void read_float_or_quotient(std::istream & is, mpq_class& et)
+  {
+    internal::read_float_or_quotient<mpz_class,mpq_class>(is, et);
+  }
+} // namespace internal
+
 } //namespace CGAL
 
 #undef CGAL_CHECK_GMP_EXPR
diff --git a/Number_types/test/Number_types/mpq_class.cpp b/Number_types/test/Number_types/mpq_class.cpp
index a6c759768b1..31b46847615 100644
--- a/Number_types/test/Number_types/mpq_class.cpp
+++ b/Number_types/test/Number_types/mpq_class.cpp
@@ -4,6 +4,7 @@
 
 #include <iostream>
 #include <CGAL/mpq_class.h>
+#include <CGAL/Lazy_exact_nt.h>
 
 #include <CGAL/Test/_test_algebraic_structure.h>
 #include <CGAL/Test/_test_real_embeddable.h>
@@ -33,6 +34,16 @@ int main() {
       mpq_class q;
       std::istringstream in("12.34");
       in >> CGAL::iformat(q);
+      assert(in);
+      assert(q.get_num() == 617);
+      assert(q.get_den() == 50);
+    }
+    {
+      CGAL::Lazy_exact_nt<mpq_class> x;
+      std::istringstream in("12.34");
+      in >> x;
+      mpq_class q = x.exact();
+      assert(in);
       assert(q.get_num() == 617);
       assert(q.get_den() == 50);
     }