diff --git a/include/boost/system/detail/system_category.hpp b/include/boost/system/detail/system_category.hpp
new file mode 100644
index 0000000..d2ddf70
--- /dev/null
+++ b/include/boost/system/detail/system_category.hpp
@@ -0,0 +1,65 @@
+#ifndef BOOST_SYSTEM_DETAIL_SYSTEM_CATEGORY_HPP_INCLUDED
+#define BOOST_SYSTEM_DETAIL_SYSTEM_CATEGORY_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/config.hpp>
+#include <boost/cstdint.hpp>
+#include <boost/config.hpp>
+#include <cstring>
+
+namespace boost
+{
+
+namespace system
+{
+
+namespace detail
+{
+
+// system_error_category
+
+#if ( defined( BOOST_GCC ) && BOOST_GCC >= 40600 ) || defined( BOOST_CLANG )
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
+#endif
+
+class BOOST_SYMBOL_VISIBLE system_error_category: public error_category
+{
+public:
+
+    BOOST_SYSTEM_CONSTEXPR system_error_category() BOOST_NOEXCEPT:
+        error_category( ( boost::ulong_long_type( 0x8FAFD21E ) << 32 ) + 0x25C5E09B )
+    {
+    }
+
+    const char * name() const BOOST_NOEXCEPT BOOST_OVERRIDE
+    {
+        return "system";
+    }
+
+    error_condition default_error_condition( int ev ) const BOOST_NOEXCEPT BOOST_OVERRIDE;
+
+    std::string message( int ev ) const BOOST_OVERRIDE;
+    char const * message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT BOOST_OVERRIDE;
+};
+
+#if ( defined( BOOST_GCC ) && BOOST_GCC >= 40600 ) || defined( BOOST_CLANG )
+#pragma GCC diagnostic pop
+#endif
+
+} // namespace detail
+
+} // namespace system
+
+} // namespace boost
+
+#endif // #ifndef BOOST_SYSTEM_DETAIL_SYSTEM_CATEGORY_HPP_INCLUDED
diff --git a/include/boost/system/error_code.hpp b/include/boost/system/error_code.hpp
index 82fbce5..1dccb4f 100644
--- a/include/boost/system/error_code.hpp
+++ b/include/boost/system/error_code.hpp
@@ -15,6 +15,7 @@
 #include <boost/system/detail/errc.hpp>
 #include <boost/system/detail/error_category.hpp>
 #include <boost/system/detail/generic_category.hpp>
+#include <boost/system/detail/system_category.hpp>
 #include <boost/system/api_config.hpp>
 #include <boost/system/detail/config.hpp>
 #include <boost/cstdint.hpp>
@@ -42,42 +43,6 @@ class error_code;         // values defined by the operating system
 class error_condition;    // portable generic values defined below, but ultimately
                           // based on the POSIX standard
 
-// predefined error categories
-
-#if ( defined( BOOST_GCC ) && BOOST_GCC >= 40600 ) || defined( BOOST_CLANG )
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
-#endif
-
-namespace detail
-{
-
-class BOOST_SYMBOL_VISIBLE system_error_category: public error_category
-{
-public:
-
-    BOOST_SYSTEM_CONSTEXPR system_error_category() BOOST_NOEXCEPT:
-        error_category( ( boost::ulong_long_type( 0x8FAFD21E ) << 32 ) + 0x25C5E09B )
-    {
-    }
-
-    const char * name() const BOOST_NOEXCEPT BOOST_OVERRIDE
-    {
-        return "system";
-    }
-
-    error_condition default_error_condition( int ev ) const BOOST_NOEXCEPT BOOST_OVERRIDE;
-
-    std::string message( int ev ) const BOOST_OVERRIDE;
-    char const * message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT BOOST_OVERRIDE;
-};
-
-} // namespace detail
-
-#if ( defined( BOOST_GCC ) && BOOST_GCC >= 40600 ) || defined( BOOST_CLANG )
-#pragma GCC diagnostic pop
-#endif
-
 // generic_category(), system_category()
 
 #if defined(BOOST_SYSTEM_HAS_CONSTEXPR)