diff --git a/lib/libsysdecode/flags.c b/lib/libsysdecode/flags.c
index bf0319f5dca..eb28820a036 100644
--- a/lib/libsysdecode/flags.c
+++ b/lib/libsysdecode/flags.c
@@ -634,8 +634,19 @@ sysdecode_quotactl_cmd(FILE *fp, int cmd)
 bool
 sysdecode_reboot_howto(FILE *fp, int howto, int *rem)
 {
+	bool printed;
 
-	return (print_mask_int(fp, rebootopt, howto, rem));
+	/*
+	 * RB_AUTOBOOT is special in that its value is zero, but it is
+	 * also an implied argument if a different operation is not
+	 * requested via RB_HALT, RB_POWEROFF, or RB_REROOT.
+	 */
+	if (howto != 0 && (howto & (RB_HALT | RB_POWEROFF | RB_REROOT)) == 0) {
+		fputs("RB_AUTOBOOT|", fp);
+		printed = true;
+	} else
+		printed = false;
+	return (print_mask_int(fp, rebootopt, howto, rem) || printed);
 }
 
 bool