diff --git a/sbin/atacontrol/atacontrol.8 b/sbin/atacontrol/atacontrol.8
index d4fd109eec21..e2daea90a986 100644
--- a/sbin/atacontrol/atacontrol.8
+++ b/sbin/atacontrol/atacontrol.8
@@ -68,8 +68,10 @@ subsystem.
 can cause severe system crashes and loss of data if used improperly, please
 exercise caution when using this command!
 .Pp
-.Nm
-supports the following commands:
+The
+.Ar channel
+argument is the number of the ata channel on which to operate.
+The following commands are supported:
 .Bl -tag -width "attach"
 .It Ic attach
 Attach an ATA
@@ -122,7 +124,7 @@ Show info about all attached devices on all active controllers.
 The
 .Nm
 utility first appeared in
-.Fx 5.0 .
+.Fx 4.6 .
 .Sh AUTHORS
 .An -nosplit
 The
diff --git a/sbin/atacontrol/atacontrol.c b/sbin/atacontrol/atacontrol.c
index 6199b3e07038..f6be45131127 100644
--- a/sbin/atacontrol/atacontrol.c
+++ b/sbin/atacontrol/atacontrol.c
@@ -242,8 +242,13 @@ main(int argc, char **argv)
 
 	bzero(&iocmd, sizeof(struct ata_cmd));
 
-	if (argc > 2)
-		iocmd.channel = atoi(argv[2]);
+	if (argc > 2) {
+		int chan;
+		if (!(sscanf(argv[2], "%d", &chan) == 1 ||
+		    sscanf(argv[2], "ata%d", &chan) == 1))
+			usage();
+		iocmd.channel = chan;
+	}
 
 	if (argc > 3)
 		master = atoi(argv[3]);