diff --git a/format.c b/format.c
index d88e583bf..839cb5096 100644
--- a/format.c
+++ b/format.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: format.c,v 1.422 2026/09/29 11:57:28 nicm Exp $ */
+/* $OpenBSD: format.c,v 1.423 2026/09/29 13:59:10 nicm Exp $ */
 
 /*
  * Copyright (c) 2011 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -4505,8 +4505,8 @@ format_pretty_time(time_t t, int seconds)
 		now = t;
 	age = now - t;
 
-	localtime_r(&now, &now_tm);
-	localtime_r(&t, &tm);
+	if (localtime_r(&now, &now_tm) == NULL || localtime_r(&t, &tm) == NULL)
+		return (xstrdup(""));
 
 	/* Last 24 hours. */
 	if (age < 24 * 3600) {
@@ -4677,10 +4677,12 @@ found:
 			found = format_pretty_time(t, 0);
 		else {
 			if (time_format != NULL) {
-				localtime_r(&t, &tm);
+				if (localtime_r(&t, &tm) == NULL)
+					return (NULL);
 				strftime(s, sizeof s, time_format, &tm);
 			} else {
-				ctime_r(&t, s);
+				if (ctime_r(&t, s) == NULL)
+					return (NULL);
 				s[strcspn(s, "\n")] = '\0';
 			}
 			found = xstrdup(s);