diff --git a/usr.bin/tmux/format.c b/usr.bin/tmux/format.c
index 2458be389d8..218e12d0ca2 100644
--- a/usr.bin/tmux/format.c
+++ b/usr.bin/tmux/format.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: format.c,v 1.358 2026/04/14 07:24:23 nicm Exp $ */
+/* $OpenBSD: format.c,v 1.359 2026/04/14 11:25:41 nicm Exp $ */
 
 /*
  * Copyright (c) 2011 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -5047,8 +5047,10 @@ format_replace(struct format_expand_state *es, const char *key, size_t keylen,
 				if (strchr(fm->argv[0], 'p') != NULL)
 					modifiers |= FORMAT_PRETTY;
 				else if (fm->argc >= 2 &&
-				    strchr(fm->argv[0], 'f') != NULL)
+				    strchr(fm->argv[0], 'f') != NULL) {
+					free(time_format);
 					time_format = format_strip(fm->argv[1]);
+				}
 				break;
 			case 'q':
 				if (fm->argc < 1)