diff --git a/src/lib/libc/string/swab.3 b/src/lib/libc/string/swab.3
index d1bfc358..628eb6b1 100644
--- a/src/lib/libc/string/swab.3
+++ b/src/lib/libc/string/swab.3
@@ -29,7 +29,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\"	$OpenBSD: swab.3,v 1.3 1998/02/10 02:19:48 deraadt Exp $
+.\"	$OpenBSD: swab.3,v 1.4 2000/01/03 22:52:59 aaron Exp $
 .\"
 .Dd May 1, 1991
 .Dt SWAB 3
@@ -54,7 +54,7 @@ swapping adjacent bytes.
 .Pp
 The argument
 .Fa len
-must be even number.
+must be an even number.
 .Sh SEE ALSO
 .Xr bzero 3 ,
 .Xr memset 3