diff --git a/tty.c b/tty.c
index ba7a5158..6dd6b490 100644
--- a/tty.c
+++ b/tty.c
@@ -778,9 +778,13 @@ tty_draw_line(struct tty *tty, const struct window_pane *wp,
 	tty_region_off(tty);
 	tty_margin_off(tty);
 
+	/*
+	 * Clamp the width to cellsize - note this is not cellused, because
+	 * there may be empty background cells after it (from BCE).
+	 */
 	sx = screen_size_x(s);
-	if (sx > s->grid->linedata[s->grid->hsize + py].cellused)
-		sx = s->grid->linedata[s->grid->hsize + py].cellused;
+	if (sx > s->grid->linedata[s->grid->hsize + py].cellsize)
+		sx = s->grid->linedata[s->grid->hsize + py].cellsize;
 	if (sx > tty->sx)
 		sx = tty->sx;