diff --git a/include/boost/integer_fwd.hpp b/include/boost/integer_fwd.hpp
index 10577ae..18519dd 100644
--- a/include/boost/integer_fwd.hpp
+++ b/include/boost/integer_fwd.hpp
@@ -159,6 +159,8 @@ template <static_min_max_unsigned_type Value1, static_min_max_unsigned_type Valu
     struct static_unsigned_max;
 
 
+namespace integer
+{
 //  From <boost/integer/common_factor_ct.hpp>
 
 #ifdef BOOST_NO_INTEGRAL_INT64_T
@@ -180,6 +182,7 @@ template < typename IntegerType >
 template < typename IntegerType >
     class lcm_evaluator;
 
+} // namespace integer
 
 }  // namespace boost