diff --git a/include/boost/system/detail/error_category_impl.hpp b/include/boost/system/detail/error_category_impl.hpp
new file mode 100644
index 0000000..af2185a
--- /dev/null
+++ b/include/boost/system/detail/error_category_impl.hpp
@@ -0,0 +1,95 @@
+#ifndef BOOST_SYSTEM_DETAIL_ERROR_CATEGORY_IMPL_HPP_INCLUDED
+#define BOOST_SYSTEM_DETAIL_ERROR_CATEGORY_IMPL_HPP_INCLUDED
+
+//  Copyright Beman Dawes 2006, 2007
+//  Copyright Christoper Kohlhoff 2007
+//  Copyright Peter Dimov 2017, 2018
+//
+//  Distributed under the Boost Software License, Version 1.0. (See accompanying
+//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+//  See library home page at http://www.boost.org/libs/system
+
+#include <boost/system/detail/error_category.hpp>
+#include <boost/system/detail/error_condition.hpp>
+#include <boost/system/detail/error_code.hpp>
+#include <boost/config.hpp>
+#include <string>
+#include <cstring>
+
+namespace boost
+{
+
+namespace system
+{
+
+// error_category default implementation
+
+inline error_condition error_category::default_error_condition( int ev ) const BOOST_NOEXCEPT
+{
+    return error_condition( ev, *this );
+}
+
+inline bool error_category::equivalent( int code, const error_condition & condition ) const BOOST_NOEXCEPT
+{
+    return default_error_condition( code ) == condition;
+}
+
+inline bool error_category::equivalent( const error_code & code, int condition ) const BOOST_NOEXCEPT
+{
+    return *this == code.category() && code.value() == condition;
+}
+
+inline char const * error_category::message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT
+{
+    if( len == 0 )
+    {
+        return buffer;
+    }
+
+    if( len == 1 )
+    {
+        buffer[0] = 0;
+        return buffer;
+    }
+
+#if !defined(BOOST_NO_EXCEPTIONS)
+    try
+#endif
+    {
+        std::string m = this->message( ev );
+
+# if defined( BOOST_MSVC )
+#  pragma warning( push )
+#  pragma warning( disable: 4996 )
+# elif defined(__clang__) && defined(__has_warning)
+#  pragma clang diagnostic push
+#  if __has_warning("-Wdeprecated-declarations")
+#   pragma clang diagnostic ignored "-Wdeprecated-declarations"
+#  endif
+# endif
+
+        std::strncpy( buffer, m.c_str(), len - 1 );
+        buffer[ len-1 ] = 0;
+
+# if defined( BOOST_MSVC )
+#  pragma warning( pop )
+# elif defined(__clang__) && defined(__has_warning)
+#  pragma clang diagnostic pop
+# endif
+
+        return buffer;
+    }
+#if !defined(BOOST_NO_EXCEPTIONS)
+    catch( ... )
+    {
+        return "Message text unavailable";
+    }
+#endif
+}
+
+} // namespace system
+
+} // namespace boost
+
+#endif // #ifndef BOOST_SYSTEM_DETAIL_ERROR_CATEGORY_IMPL_HPP_INCLUDED
diff --git a/include/boost/system/error_code.hpp b/include/boost/system/error_code.hpp
index ef0fdab..de95b13 100644
--- a/include/boost/system/error_code.hpp
+++ b/include/boost/system/error_code.hpp
@@ -20,6 +20,7 @@
 #include <boost/system/detail/error_condition.hpp>
 #include <boost/system/detail/error_code.hpp>
 #include <boost/system/detail/throws.hpp>
+#include <boost/system/detail/error_category_impl.hpp>
 #include <boost/system/api_config.hpp>
 #include <boost/system/detail/config.hpp>
 #include <boost/cstdint.hpp>
@@ -93,71 +94,6 @@ BOOST_SYSTEM_CONSTEXPR inline error_condition make_error_condition( errc_t e ) B
 
 } // namespace errc
 
-// error_category default implementation
-
-inline error_condition error_category::default_error_condition( int ev ) const BOOST_NOEXCEPT
-{
-    return error_condition( ev, *this );
-}
-
-inline bool error_category::equivalent( int code, const error_condition & condition ) const BOOST_NOEXCEPT
-{
-    return default_error_condition( code ) == condition;
-}
-
-inline bool error_category::equivalent( const error_code & code, int condition ) const BOOST_NOEXCEPT
-{
-    return *this == code.category() && code.value() == condition;
-}
-
-inline char const * error_category::message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT
-{
-    if( len == 0 )
-    {
-        return buffer;
-    }
-
-    if( len == 1 )
-    {
-        buffer[0] = 0;
-        return buffer;
-    }
-
-#if !defined(BOOST_NO_EXCEPTIONS)
-    try
-#endif
-    {
-        std::string m = this->message( ev );
-
-# if defined( BOOST_MSVC )
-#  pragma warning( push )
-#  pragma warning( disable: 4996 )
-# elif defined(__clang__) && defined(__has_warning)
-#  pragma clang diagnostic push
-#  if __has_warning("-Wdeprecated-declarations")
-#   pragma clang diagnostic ignored "-Wdeprecated-declarations"
-#  endif
-# endif
-
-        std::strncpy( buffer, m.c_str(), len - 1 );
-        buffer[ len-1 ] = 0;
-
-# if defined( BOOST_MSVC )
-#  pragma warning( pop )
-# elif defined(__clang__) && defined(__has_warning)
-#  pragma clang diagnostic pop
-# endif
-
-        return buffer;
-    }
-#if !defined(BOOST_NO_EXCEPTIONS)
-    catch( ... )
-    {
-        return "Message text unavailable";
-    }
-#endif
-}
-
 } // namespace system
 
 } // namespace boost