diff --git a/bin/pkill/pkill.c b/bin/pkill/pkill.c
--- a/bin/pkill/pkill.c
+++ b/bin/pkill/pkill.c
@@ -827,6 +827,20 @@
 		usage();
 }
 
+static int
+pidmax(void)
+{
+	int val;
+	size_t size;
+
+	size = sizeof(val);
+	if (sysctlbyname("kern.pid_max", &val, &size, NULL, 0) < 0) {
+		return (PID_MAX);
+	}
+
+	return (val);
+}
+
 static int
 takepid(const char *pidfile, int pidfilelock)
 {
@@ -867,7 +881,7 @@
 	rval = strtol(line, &endp, 10);
 	if (*endp != '\0' && !isspace((unsigned char)*endp))
 		errx(STATUS_ERROR, "Invalid pid in file `%s'", pidfile);
-	else if (rval < PID_MIN || rval > PID_MAX)
+	else if (rval < PID_MIN || rval > pidmax())
 		errx(STATUS_ERROR, "Invalid pid in file `%s'", pidfile);
 	return (rval);
 }