diff --git a/usr.bin/cpuset/cpuset.1 b/usr.bin/cpuset/cpuset.1
index 00f9e81b823f..b97234a274e7 100644
--- a/usr.bin/cpuset/cpuset.1
+++ b/usr.bin/cpuset/cpuset.1
@@ -89,8 +89,12 @@ queried using
 When running a command it may join a set specified with
 .Fl s
 otherwise a new set is created.
-In addition, a mask for the set may be specified using
+In addition, a mask for the command may be specified using
 .Fl l .
+When used in conjunction with
+.Fl c
+the mask modifies the supplied or created set rather than the private mask
+for the thread.
 .Pp
 The options are as follows:
 .Bl -tag -width ".Fl l Ar cpu-list"
@@ -127,7 +131,7 @@ Specifies a thread id as the target of the operation.
 Create a new group with CPUs 0-4 inclusive and run
 .Pa /bin/sh
 on it:
-.Dl cpuset -l 0-4 /bin/sh
+.Dl cpuset -c -l 0-4 /bin/sh
 .Pp
 Query the mask of CPUs the
 .Aq sh pid
diff --git a/usr.bin/cpuset/cpuset.c b/usr.bin/cpuset/cpuset.c
index 41a715dff9e9..c31ebb7fb04f 100644
--- a/usr.bin/cpuset/cpuset.c
+++ b/usr.bin/cpuset/cpuset.c
@@ -257,7 +257,7 @@ main(int argc, char *argv[])
 	 * The user wants to run a command with a set and possibly cpumask.
 	 */
 	if (argc) {
-		if (pflag | rflag | tflag || cflag)
+		if (pflag | rflag | tflag)
 			usage();
 		if (sflag) {
 			if (cpuset_setid(CPU_WHICH_PID, -1, setid))
@@ -267,7 +267,7 @@ main(int argc, char *argv[])
 				err(argc, "newid");
 		}
 		if (lflag) {
-			if (cpuset_setaffinity(CPU_LEVEL_CPUSET, CPU_WHICH_PID,
+			if (cpuset_setaffinity(level, CPU_WHICH_PID,
 			    -1, sizeof(mask), &mask) != 0)
 				err(EXIT_FAILURE, "setaffinity");
 		}