diff --git a/input.c b/input.c
index ed1ebffc..19fd48b7 100644
--- a/input.c
+++ b/input.c
@@ -100,7 +100,7 @@ struct input_ctx {
 struct input_transition;
 int	input_split(struct input_ctx *);
 int	input_get(struct input_ctx *, u_int, int, int);
-void	input_reply(struct input_ctx *, const char *, ...);
+void printflike(2, 3) input_reply(struct input_ctx *, const char *, ...);
 void	input_set_state(struct window_pane *, const struct input_transition *);
 void	input_reset_cell(struct input_ctx *);
 
diff --git a/tmux.h b/tmux.h
index 194d01d8..dbea85bf 100644
--- a/tmux.h
+++ b/tmux.h
@@ -1540,7 +1540,7 @@ extern struct client *cfg_client;
 void		 start_cfg(void);
 int		 load_cfg(const char *, struct cmd_q *, char **);
 void		 set_cfg_file(const char *);
-void		 cfg_add_cause(const char *, ...);
+void printflike(1, 2) cfg_add_cause(const char *, ...);
 void		 cfg_print_causes(struct cmd_q *);
 void		 cfg_show_causes(struct session *);