diff --git a/include/boost/numeric/interval/detail/c99sub_rounding_control.hpp b/include/boost/numeric/interval/detail/c99sub_rounding_control.hpp
index a8684df..00084c9 100644
--- a/include/boost/numeric/interval/detail/c99sub_rounding_control.hpp
+++ b/include/boost/numeric/interval/detail/c99sub_rounding_control.hpp
@@ -18,7 +18,7 @@ namespace numeric {
 namespace interval_lib {
 namespace detail {
 
-extern "C" { double rint(double); }
+extern "C" { double rint(double); long double rintl(long double); }
 
 struct c99_rounding_control
 {
@@ -33,6 +33,7 @@ struct c99_rounding_control
 
   template<class T>
   static T to_int(const T& r) { return rint(r); }
+  static long double to_int(const long double& r) { return rintl(r); }
 };
 
 } // namespace detail
diff --git a/include/boost/numeric/interval/detail/ppc_rounding_control.hpp b/include/boost/numeric/interval/detail/ppc_rounding_control.hpp
index f7e6781..45d3e6d 100644
--- a/include/boost/numeric/interval/detail/ppc_rounding_control.hpp
+++ b/include/boost/numeric/interval/detail/ppc_rounding_control.hpp
@@ -64,6 +64,7 @@ struct ppc_rounding_control
 extern "C" {
   float rintf(float);
   double rint(double);
+  long double rintl(long double);
 }
 #endif
 
@@ -114,7 +115,7 @@ struct rounding_control<long double>:
 #endif
     return r_;
   }
-  static long double to_int(const long double& r) { return rint(r); }
+  static long double to_int(const long double& r) { return rintl(r); }
 };
 
 } // namespace interval_lib
diff --git a/include/boost/numeric/interval/detail/sparc_rounding_control.hpp b/include/boost/numeric/interval/detail/sparc_rounding_control.hpp
index 2b08bec..88e557e 100644
--- a/include/boost/numeric/interval/detail/sparc_rounding_control.hpp
+++ b/include/boost/numeric/interval/detail/sparc_rounding_control.hpp
@@ -77,6 +77,7 @@ struct sparc_rounding_control
 extern "C" {
   float rintf(float);
   double rint(double);
+  long double rintl(long double);
 }
 
 template<>
@@ -100,7 +101,7 @@ struct rounding_control<long double>:
   detail::sparc_rounding_control
 {
   static const long double& force_rounding(const long double& x) { return x; }
-  static long double to_int(const long double& x) { return rint(x); }
+  static long double to_int(const long double& x) { return rintl(x); }
 };
 
 } // namespace interval_lib
diff --git a/test/fmod.cpp b/test/fmod.cpp
index 11e88ed..40a5f00 100644
--- a/test/fmod.cpp
+++ b/test/fmod.cpp
@@ -14,6 +14,7 @@
 #include <boost/numeric/interval/utility.hpp>
 #include <boost/numeric/interval/checking.hpp>
 #include <boost/numeric/interval/rounding.hpp>
+#include <boost/numeric/interval/hw_rounding.hpp>
 #include <boost/core/lightweight_test.hpp>
 #include "bugs.hpp"
 
@@ -35,6 +36,15 @@ using namespace interval_lib;
 
 typedef change_rounding<interval<int>, save_state_nothing<my_rounded_arith> >::type I;
 
+// to_int must round a long double with rintl: rint converts it to double
+// first, and fmod(2^60 + 1, 1) then misses 0.
+void test_long_double() {
+  typedef interval<long double> L;
+  if (std::numeric_limits<long double>::digits < 62) return;
+  long double big = 1152921504606846977.0L, one = 1;  // 2^60 + 1
+  BOOST_TEST(in_zero(fmod(L(big), L(one))));
+}
+
 int main() {
 
   BOOST_TEST(equal(fmod(I(6,9), 7), I(6,9)));
@@ -49,5 +59,7 @@ int main() {
   BOOST_TEST(equal(fmod(-17, I(7,8)), I(4,7)));
   BOOST_TEST(equal(fmod(I(-17,-13), I(7,8)), I(4,11)));
 
+  test_long_double();
+
   return boost::report_errors();
 }