diff --git a/usr.bin/tmux/layout-custom.c b/usr.bin/tmux/layout-custom.c
index 7833938f0a6..2ddfb97c7e2 100644
--- a/usr.bin/tmux/layout-custom.c
+++ b/usr.bin/tmux/layout-custom.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: layout-custom.c,v 1.24 2026/04/04 16:40:27 nicm Exp $ */
+/* $OpenBSD: layout-custom.c,v 1.25 2026/05/07 09:21:05 nicm Exp $ */
 
 /*
  * Copyright (c) 2010 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -160,13 +160,14 @@ layout_parse(struct window *w, const char *layout, char **cause)
 	struct window_pane	*wp;
 	u_int			 npanes, ncells, sx = 0, sy = 0;
 	u_short			 csum;
+	int			 n;
 
 	/* Check validity. */
-	if (sscanf(layout, "%hx,", &csum) != 1) {
+	if (sscanf(layout, "%hx,%n", &csum, &n) != 1 || n != 5) {
 		*cause = xstrdup("invalid layout");
 		return (-1);
 	}
-	layout += 5;
+	layout += n;
 	if (csum != layout_checksum(layout)) {
 		*cause = xstrdup("invalid layout");
 		return (-1);
diff --git a/usr.bin/tmux/window-copy.c b/usr.bin/tmux/window-copy.c
index 1f2b89dca56..5ed2791d857 100644
--- a/usr.bin/tmux/window-copy.c
+++ b/usr.bin/tmux/window-copy.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: window-copy.c,v 1.397 2026/05/07 09:15:44 nicm Exp $ */
+/* $OpenBSD: window-copy.c,v 1.398 2026/05/07 09:21:05 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -469,7 +469,7 @@ window_copy_init(struct window_mode_entry *wme,
 	struct screen			*base = &wp->base;
 	struct screen_write_ctx		 ctx;
 	u_int				 i, cx, cy;
-	
+
 	data = window_copy_common_init(wme);
 	data->backing = window_copy_clone_screen(base, &data->screen, &cx, &cy,
 	    wme->swp != wme->wp);