--- /usr/src/usr.sbin/arp/arp.8	2008-04-28 10:52:02.000000000 +0200
+++ /usr/src/usr.sbin/arp/arp.8	2008-07-23 10:06:31.000000000 +0200
@@ -53,14 +53,12 @@
 .Nm
 .Fl s Ar hostname ether_addr
 .Op Cm temp
-.Op Cm reject
-.Op Cm blackhole
+.Op Cm blackhole No \&| Cm reject
 .Op Cm pub Op Cm only
 .Nm
 .Fl S Ar hostname ether_addr
 .Op Cm temp
-.Op Cm reject
-.Op Cm blackhole
+.Op Cm blackhole No \&| Cm reject
 .Op Cm pub Op Cm only
 .Nm
 .Fl f Ar filename
@@ -182,7 +180,8 @@
 .Bd -ragged -offset indent -compact
 .Ar hostname ether_addr
 .Op Cm temp
-.Op Cm pub
+.Op Cm blackhole No \&| Cm reject
+.Op Cm pub Op Cm only
 .Ed
 .Pp
 with argument meanings as given above.
--- /usr/src/usr.sbin/arp/arp.c	2008-04-25 18:38:14.000000000 +0200
+++ /usr/src/usr.sbin/arp/arp.c	2008-07-23 10:18:35.000000000 +0200
@@ -330,8 +330,14 @@
 				argc--; argv++;
 			}
 		} else if (strncmp(argv[0], "blackhole", 9) == 0) {
+			if (flags & RTF_REJECT) {
+				printf("Choose one of blackhole or reject, not both.\n");
+			}
 			flags |= RTF_BLACKHOLE;
 		} else if (strncmp(argv[0], "reject", 6) == 0) {
+			if (flags & RTF_BLACKHOLE) {
+				printf("Choose one of blackhole or reject, not both.\n");
+			}
 			flags |= RTF_REJECT;
 		} else if (strncmp(argv[0], "trail", 5) == 0) {
 			/* XXX deprecated and undocumented feature */
@@ -630,8 +636,8 @@
 		"       arp [-n] [-i interface] -a",
 		"       arp -d hostname [pub]",
 		"       arp -d [-i interface] -a",
-		"       arp -s hostname ether_addr [temp] [reject] [blackhole] [pub [only]]",
-		"       arp -S hostname ether_addr [temp] [reject] [blackhole] [pub [only]]",
+		"       arp -s hostname ether_addr [temp] [reject | blackhole] [pub [only]]",
+		"       arp -S hostname ether_addr [temp] [reject | blackhole] [pub [only]]",
 		"       arp -f filename");
 	exit(1);
 }