diff --git a/usr.bin/killall/killall.c b/usr.bin/killall/killall.c
index 13dc55688cd3..b171630d6b9b 100644
--- a/usr.bin/killall/killall.c
+++ b/usr.bin/killall/killall.c
@@ -90,6 +90,7 @@ nosig(char *name)
 int
 main(int ac, char **av)
 {
+	char		**saved_av;
 	struct kinfo_proc *procs, *newprocs;
 	struct stat	sb;
 	struct passwd	*pw;
@@ -210,16 +211,8 @@ main(int ac, char **av)
 			case 'z':
 				zflag++;
 				break;
-			case 'I':
-				/*
-				 * NB: do not confuse -INT with -I
-				 */
-				if (strncmp(*av, "INT", 3) != 0) {
-					Iflag = 1;
-					break;
-				}
-				/* FALLTHROUGH */
 			default:
+				saved_av = av;
 				if (isalpha((unsigned char)**av)) {
 					if (strncasecmp(*av, "SIG", 3) == 0)
 						*av += 3;
@@ -229,8 +222,14 @@ main(int ac, char **av)
 							sig = p - sys_signame;
 							break;
 						}
-					if (!sig)
-						nosig(*av);
+					if (!sig) {
+						if (**saved_av == 'I') {
+							av = saved_av;
+							Iflag = 1;
+							break;
+						} else
+							nosig(*av);
+					}
 				} else if (isdigit((unsigned char)**av)) {
 					sig = strtol(*av, &ep, 10);
 					if (!*av || *ep)