diff --git a/include/libtorrent/config.hpp b/include/libtorrent/config.hpp
index c898cd787..951ff0fec 100644
--- a/include/libtorrent/config.hpp
+++ b/include/libtorrent/config.hpp
@@ -133,7 +133,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #elif defined sun || defined __sun 
 #define TORRENT_SOLARIS
 #else
-#warning unkown OS, assuming BSD
+#warning unknown OS, assuming BSD
 #define TORRENT_BSD
 #endif