diff --git a/utils/idmapd/idmapd.c b/utils/idmapd/idmapd.c
index aff89d1..f55d2e1 100644
--- a/utils/idmapd/idmapd.c
+++ b/utils/idmapd/idmapd.c
@@ -199,6 +199,12 @@ flush_nfsd_idmap_cache(void)
 	return ret;
 }
 
+void usage(char *progname)
+{
+	fprintf(stderr, "Usage: %s [-hfvCS] [-p path] [-c path]\n",
+		basename(progname));
+}
+
 int
 main(int argc, char **argv)
 {
@@ -225,16 +231,18 @@ main(int argc, char **argv)
 		progname = argv[0];
 	xlog_open(progname);
 
-#define GETOPTSTR "vfd:p:U:G:c:CS"
+#define GETOPTSTR "hvfd:p:U:G:c:CS"
 	opterr=0; /* Turn off error messages */
 	while ((opt = getopt(argc, argv, GETOPTSTR)) != -1) {
 		if (opt == 'c')
 			conf_path = optarg;
 		if (opt == '?') {
 			if (strchr(GETOPTSTR, optopt))
-				errx(1, "'-%c' option requires an argument.", optopt);
+				warnx("'-%c' option requires an argument.", optopt);
 			else
-				errx(1, "'-%c' is an invalid argument.", optopt);
+				warnx("'-%c' is an invalid argument.", optopt);
+			usage(progname);
+			exit(1);
 		}
 	}
 	optind = 1;
@@ -276,6 +284,9 @@ main(int argc, char **argv)
 		case 'S':
 			clientstart = 0;
 			break;
+		case 'h':
+			usage(progname);
+			exit(0);
 		default:
 			break;
 		}
diff --git a/utils/idmapd/idmapd.man b/utils/idmapd/idmapd.man
index 185cd1b..b9200c7 100644
--- a/utils/idmapd/idmapd.man
+++ b/utils/idmapd/idmapd.man
@@ -10,8 +10,11 @@
 .Sh SYNOPSIS
 .\" For a program:  program [-abc] file ...
 .Nm rpc.idmapd
-.Op Fl v
+.Op Fl h
 .Op Fl f
+.Op Fl v
+.Op Fl C
+.Op Fl S
 .Op Fl p Ar path
 .Op Fl c Ar path
 .Sh DESCRIPTION
@@ -20,8 +23,20 @@ is the NFSv4 ID <-> name mapping daemon.  It provides functionality to
 the NFSv4 kernel client and server, to which it communicates via
 upcalls, by translating user and group IDs to names, and vice versa.
 .Pp
+Note that on more recent kernels only the NFSv4 server uses
+.Nm .
+The NFSv4 client instead uses
+.Xr nfsidmap 8 ,
+and only falls back to 
+.Nm 
+if there was a problem running the
+.Xr nfsidmap 8
+program.
+.Pp
 The options are as follows:
 .Bl -tag -width Ds_imagedir
+.It Fl h
+Display usage message.
 .It Fl v
 Increases the verbosity level (can be specified multiple times).
 .It Fl f
@@ -58,7 +73,8 @@ messages to console, and with a verbosity level of 3.
 .Sh FILES
 .Pa /etc/idmapd.conf
 .Sh SEE ALSO
-.Xr idmapd.conf 5
+.Xr idmapd.conf 5 ,
+.Xr nfsidmap 8
 .\".Sh SEE ALSO
 .\".Xr nylon.conf 4
 .\" .Sh COMPATIBILITY