diff --git a/format.c b/format.c
index 633be101..269d506a 100644
--- a/format.c
+++ b/format.c
@@ -1154,7 +1154,9 @@ format_defaults_client(struct format_tree *ft, struct client *c)
 
 	format_add_tv(ft, "client_created", &c->creation_time);
 	format_add_tv(ft, "client_activity", &c->activity_time);
-	format_add(ft, "client_written", "%zu", tty->written);
+
+	format_add(ft, "client_written", "%zu", c->written);
+	format_add(ft, "client_discarded", "%zu", c->discarded);
 
 	name = server_client_get_key_table(c);
 	if (strcmp(c->keytable->name, name) == 0)
diff --git a/server-client.c b/server-client.c
index 2279d43a..f4fc915b 100644
--- a/server-client.c
+++ b/server-client.c
@@ -1269,8 +1269,8 @@ server_client_check_redraw(struct client *c)
 		screen_redraw_update(c); /* will adjust flags */
 	}
 
-	flags = tty->flags & (TTY_FREEZE|TTY_NOCURSOR);
-	tty->flags = (tty->flags & ~TTY_FREEZE) | TTY_NOCURSOR;
+	flags = tty->flags & (TTY_BLOCK|TTY_FREEZE|TTY_NOCURSOR);
+	tty->flags = (tty->flags & ~(TTY_BLOCK|TTY_FREEZE)) | TTY_NOCURSOR;
 
 	if (c->flags & CLIENT_REDRAW) {
 		tty_update_mode(tty, tty->mode, NULL);
diff --git a/tmux.1 b/tmux.1
index d4330d18..681c2381 100644
--- a/tmux.1
+++ b/tmux.1
@@ -3508,6 +3508,7 @@ The following variables are available, where appropriate:
 .It Li "client_activity" Ta "" Ta "Integer time client last had activity"
 .It Li "client_created" Ta "" Ta "Integer time client created"
 .It Li "client_control_mode" Ta "" Ta "1 if client is in control mode"
+.It Li "client_discarded" Ta "" Ta "Bytes discarded when client behind"
 .It Li "client_height" Ta "" Ta "Height of client"
 .It Li "client_key_table" Ta "" Ta "Current key table"
 .It Li "client_last_session" Ta "" Ta "Name of the client's last session"
diff --git a/tmux.h b/tmux.h
index 3387798f..ac279123 100644
--- a/tmux.h
+++ b/tmux.h
@@ -1043,7 +1043,8 @@ struct tty {
 	struct evbuffer	*in;
 	struct event	 event_out;
 	struct evbuffer	*out;
-	size_t		 written;
+	struct event	 timer;
+	size_t		 discarded;
 
 	struct termios	 tio;
 
@@ -1059,6 +1060,7 @@ struct tty {
 #define TTY_STARTED 0x10
 #define TTY_OPENED 0x20
 #define TTY_FOCUS 0x40
+#define TTY_BLOCK 0x80
 	int		 flags;
 
 	struct tty_term	*term;
@@ -1306,6 +1308,9 @@ struct client {
 	char		*ttyname;
 	struct tty	 tty;
 
+	size_t		 written;
+	size_t		 discarded;
+
 	void		(*stdin_callback)(struct client *, int, void *);
 	void		*stdin_callback_data;
 	struct evbuffer	*stdin_data;
diff --git a/tty.c b/tty.c
index 73aeb91f..362cd36c 100644
--- a/tty.c
+++ b/tty.c
@@ -79,6 +79,10 @@ static void	tty_default_attributes(struct tty *, const struct window_pane *,
 #define tty_pane_full_width(tty, ctx) \
 	((ctx)->xoff == 0 && screen_size_x((ctx)->wp->screen) >= (tty)->sx)
 
+#define TTY_BLOCK_INTERVAL (100000 /* 100 milliseconds */)
+#define TTY_BLOCK_START(tty) (1 + ((tty)->sx * (tty)->sy) * 8)
+#define TTY_BLOCK_STOP(tty) (1 + ((tty)->sx * (tty)->sy) / 8)
+
 void
 tty_create_log(void)
 {
@@ -171,6 +175,51 @@ tty_read_callback(__unused int fd, __unused short events, void *data)
 		;
 }
 
+static void
+tty_timer_callback(__unused int fd, __unused short events, void *data)
+{
+	struct tty	*tty = data;
+	struct client	*c = tty->client;
+	struct timeval	 tv = { .tv_usec = TTY_BLOCK_INTERVAL };
+
+	log_debug("%s: %zu discarded", c->name, tty->discarded);
+
+	c->flags |= CLIENT_REDRAW;
+	c->discarded += tty->discarded;
+
+	if (tty->discarded < TTY_BLOCK_STOP(tty)) {
+		tty->flags &= ~TTY_BLOCK;
+		tty_invalidate(tty);
+		return;
+	}
+	tty->discarded = 0;
+	evtimer_add(&tty->timer, &tv);
+}
+
+static int
+tty_block_maybe(struct tty *tty)
+{
+	struct client	*c = tty->client;
+	size_t		 size = EVBUFFER_LENGTH(tty->out);
+	struct timeval	 tv = { .tv_usec = TTY_BLOCK_INTERVAL };
+
+	if (size < TTY_BLOCK_START(tty))
+		return (0);
+
+	if (tty->flags & TTY_BLOCK)
+		return (1);
+	tty->flags |= TTY_BLOCK;
+
+	log_debug("%s: can't keep up, %zu discarded", c->name, size);
+
+	evbuffer_drain(tty->out, size);
+	c->discarded += size;
+
+	tty->discarded = 0;
+	evtimer_add(&tty->timer, &tv);
+	return (1);
+}
+
 static void
 tty_write_callback(__unused int fd, __unused short events, void *data)
 {
@@ -184,6 +233,9 @@ tty_write_callback(__unused int fd, __unused short events, void *data)
 		return;
 	log_debug("%s: wrote %d bytes (of %zu)", c->name, nwrite, size);
 
+	if (tty_block_maybe(tty))
+		return;
+
 	if (EVBUFFER_LENGTH(tty->out) != 0)
 		event_add(&tty->event_out, NULL);
 }
@@ -198,7 +250,7 @@ tty_open(struct tty *tty, char **cause)
 	}
 	tty->flags |= TTY_OPENED;
 
-	tty->flags &= ~(TTY_NOCURSOR|TTY_FREEZE);
+	tty->flags &= ~(TTY_NOCURSOR|TTY_FREEZE|TTY_BLOCK|TTY_TIMER);
 
 	event_set(&tty->event_in, tty->fd, EV_PERSIST|EV_READ,
 	    tty_read_callback, tty);
@@ -207,6 +259,8 @@ tty_open(struct tty *tty, char **cause)
 	event_set(&tty->event_out, tty->fd, EV_WRITE, tty_write_callback, tty);
 	tty->out = evbuffer_new();
 
+	evtimer_set(&tty->timer, tty_timer_callback, tty);
+
 	tty_start_tty(tty);
 
 	tty_keys_build(tty);
@@ -273,6 +327,9 @@ tty_stop_tty(struct tty *tty)
 		return;
 	tty->flags &= ~TTY_STARTED;
 
+	event_del(&tty->timer);
+	tty->flags &= ~TTY_BLOCK;
+
 	event_del(&tty->event_in);
 	event_del(&tty->event_out);
 
@@ -425,9 +482,14 @@ tty_add(struct tty *tty, const char *buf, size_t len)
 {
 	struct client	*c = tty->client;
 
+	if (tty->flags & TTY_BLOCK) {
+		tty->discarded += len;
+		return;
+	}
+
 	evbuffer_add(tty->out, buf, len);
 	log_debug("%s: %.*s", c->name, (int)len, (const char *)buf);
-	tty->written += len;
+	c->written += len;
 
 	if (tty_log_fd != -1)
 		write(tty_log_fd, buf, len);