diff --git a/include/boost/system/detail/error_category_impl.hpp b/include/boost/system/detail/error_category_impl.hpp
index 9ab0e49..66f2f60 100644
--- a/include/boost/system/detail/error_category_impl.hpp
+++ b/include/boost/system/detail/error_category_impl.hpp
@@ -13,6 +13,7 @@
 #include <boost/system/detail/error_category.hpp>
 #include <boost/system/detail/error_condition.hpp>
 #include <boost/system/detail/error_code.hpp>
+#include <boost/system/detail/snprintf.hpp>
 #include <boost/config.hpp>
 #include <string>
 #include <cstring>
@@ -83,7 +84,8 @@ inline char const * error_category::message( int ev, char * buffer, std::size_t
 #if !defined(BOOST_NO_EXCEPTIONS)
     catch( ... )
     {
-        return "Message text unavailable";
+        detail::snprintf( buffer, len, "No message text available for error %d", ev );
+        return buffer;
     }
 #endif
 }
diff --git a/include/boost/system/detail/snprintf.hpp b/include/boost/system/detail/snprintf.hpp
new file mode 100644
index 0000000..d077102
--- /dev/null
+++ b/include/boost/system/detail/snprintf.hpp
@@ -0,0 +1,70 @@
+#ifndef BOOST_SYSTEM_DETAIL_SNPRINTF_HPP_INCLUDED
+#define BOOST_SYSTEM_DETAIL_SNPRINTF_HPP_INCLUDED
+
+// Copyright 2018, 2020, 2021 Peter Dimov
+//
+// 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/config.hpp>
+#include <cstdio>
+#include <cstdarg>
+
+//
+
+namespace boost
+{
+
+namespace system
+{
+
+namespace detail
+{
+
+#if ( defined(_MSC_VER) && _MSC_VER < 1900 ) || ( defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR) )
+
+inline void snprintf( char * buffer, std::size_t len, char const * format, ... )
+{
+# if defined( BOOST_MSVC )
+#  pragma warning( push )
+#  pragma warning( disable: 4996 )
+# endif
+
+    if( len == 0 ) return;
+
+    va_list args;
+    va_start( args, format );
+
+    _vsnprintf( buffer, len - 1, format, args );
+    buffer[ len - 1 ] = 0;
+
+    va_end( args );
+
+# if defined( BOOST_MSVC )
+#  pragma warning( pop )
+# endif
+}
+
+#else
+
+inline void snprintf( char * buffer, std::size_t len, char const * format, ... )
+{
+    va_list args;
+    va_start( args, format );
+
+    std::vsnprintf( buffer, len, format, args );
+
+    va_end( args );
+}
+
+#endif
+
+} // namespace detail
+
+} // namespace system
+
+} // namespace boost
+
+#endif // #ifndef BOOST_SYSTEM_DETAIL_SNPRINTF_HPP_INCLUDED
diff --git a/include/boost/system/detail/system_category_message_win32.hpp b/include/boost/system/detail/system_category_message_win32.hpp
index 6cdec2d..e5f544c 100644
--- a/include/boost/system/detail/system_category_message_win32.hpp
+++ b/include/boost/system/detail/system_category_message_win32.hpp
@@ -10,6 +10,7 @@
 //
 // See library home page at http://www.boost.org/libs/system
 
+#include <boost/system/detail/snprintf.hpp>
 #include <boost/winapi/error_handling.hpp>
 #include <boost/winapi/character_code_conversion.hpp>
 #include <boost/winapi/local_memory.hpp>
@@ -27,35 +28,12 @@ namespace system
 namespace detail
 {
 
-#if ( defined(_MSC_VER) && _MSC_VER < 1900 ) || ( defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR) )
-
 inline char const * unknown_message_win32( int ev, char * buffer, std::size_t len )
 {
-# if defined( BOOST_MSVC )
-#  pragma warning( push )
-#  pragma warning( disable: 4996 )
-# endif
-
-    _snprintf( buffer, len - 1, "Unknown error (%d)", ev );
-
-    buffer[ len - 1 ] = 0;
-    return buffer;
-
-# if defined( BOOST_MSVC )
-#  pragma warning( pop )
-# endif
-}
-
-#else
-
-inline char const * unknown_message_win32( int ev, char * buffer, std::size_t len )
-{
-    std::snprintf( buffer, len, "Unknown error (%d)", ev );
+    detail::snprintf( buffer, len, "Unknown error (%d)", ev );
     return buffer;
 }
 
-#endif
-
 inline boost::winapi::UINT_ message_cp_win32()
 {
 #if defined(BOOST_SYSTEM_USE_UTF8)
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 23b0b17..4dd3ab8 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -87,3 +87,5 @@ boost_test(TYPE run SOURCES cygwin_error_test.cpp)
 boost_test(TYPE run SOURCES linux_error_test.cpp)
 
 boost_test(TYPE link SOURCES errc_test3.cpp)
+
+boost_test(TYPE run SOURCES snprintf_test.cpp)
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 0998571..3061abe 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -91,3 +91,5 @@ run cygwin_error_test.cpp ;
 run linux_error_test.cpp ;
 
 link errc_test3.cpp ;
+
+run snprintf_test.cpp ;
diff --git a/test/snprintf_test.cpp b/test/snprintf_test.cpp
new file mode 100644
index 0000000..02e6f75
--- /dev/null
+++ b/test/snprintf_test.cpp
@@ -0,0 +1,60 @@
+// Copyright 2021 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/system/detail/snprintf.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+int main()
+{
+    {
+        char buffer[ 64 ];
+        boost::system::detail::snprintf( buffer, sizeof(buffer), "...%s...%d...", "xy", 151 );
+
+        BOOST_TEST_CSTR_EQ( buffer, "...xy...151..." );
+    }
+
+    {
+        char buffer[ 64 ];
+        boost::system::detail::snprintf( buffer, sizeof(buffer), "...%s...%d...", "xy", 151 );
+
+        BOOST_TEST_CSTR_EQ( buffer, "...xy...151..." );
+    }
+
+    {
+        char buffer[ 15 ];
+        boost::system::detail::snprintf( buffer, sizeof(buffer), "...%s...%d...", "xy", 151 );
+
+        BOOST_TEST_CSTR_EQ( buffer, "...xy...151..." );
+    }
+
+    {
+        char buffer[ 14 ];
+        boost::system::detail::snprintf( buffer, sizeof(buffer), "...%s...%d...", "xy", 151 );
+
+        BOOST_TEST_CSTR_EQ( buffer, "...xy...151.." );
+    }
+
+    {
+        char buffer[ 5 ];
+        boost::system::detail::snprintf( buffer, sizeof(buffer), "...%s...%d...", "xy", 151 );
+
+        BOOST_TEST_CSTR_EQ( buffer, "...x" );
+    }
+
+    {
+        char buffer[ 1 ];
+        boost::system::detail::snprintf( buffer, sizeof(buffer), "...%s...%d...", "xy", 151 );
+
+        BOOST_TEST_CSTR_EQ( buffer, "" );
+    }
+
+    {
+        char buffer[ 1 ] = { 'Q' };
+        boost::system::detail::snprintf( buffer, 0, "...%s...%d...", "xy", 151 );
+
+        BOOST_TEST_EQ( buffer[0], 'Q' );
+    }
+
+    return boost::report_errors();
+}