diff --git a/screen-redraw.c b/screen-redraw.c
index 7e54607b..2fcfe43b 100644
--- a/screen-redraw.c
+++ b/screen-redraw.c
@@ -461,16 +461,16 @@ screen_redraw_check_cell(struct screen_redraw_ctx *ctx, u_int px, u_int py,
 			wp->scrollbar_style.pad;
 		if (sb_pos == PANE_SCROLLBARS_LEFT) {
 			if (~wp->flags & PANE_MINIMISED &&
-			    ((int)px >= wp->xoff - 1 - sb_w &&
+			    ((int)px >= (int)wp->xoff - 1 - sb_w &&
 			    (int)px <= wp->xoff + (int)wp->sx) &&
-			    ((int)py >= wp->yoff - 1 &&
+			    ((int)py >= (int)wp->yoff - 1 &&
 			    (int)py <= wp->yoff + (int)wp->sy))
 				break;
 		} else { /* PANE_SCROLLBARS_RIGHT or none. */
 			if (~wp->flags & PANE_MINIMISED &&
-			    ((int)px >= wp->xoff - 1 &&
+			    ((int)px >= (int)wp->xoff - 1 &&
 			    (int)px <= wp->xoff + (int)wp->sx + sb_w) &&
-			    ((int)py >= wp->yoff - 1 &&
+			    ((int)py >= (int)wp->yoff - 1 &&
 			    (int)py <= wp->yoff + (int)wp->sy))
 				break;
 		}
@@ -1178,7 +1178,7 @@ screen_redraw_get_visible_ranges(struct window_pane *base_wp, u_int px,
 			continue;
 		}
 
-		tb = wp->yoff - 1;
+		tb = (wp->yoff > 0) ? wp->yoff - 1 : 0;
 		bb = wp->yoff + wp->sy;
 		if (!found_self ||
 		    !window_pane_visible(wp) ||
diff --git a/screen-write.c b/screen-write.c
index 92759adc..dbfc8b3c 100644
--- a/screen-write.c
+++ b/screen-write.c
@@ -1991,9 +1991,14 @@ screen_write_pane_obscured(struct window_pane *base_wp)
 		    ((wp->xoff >= base_wp->xoff &&
 		    wp->xoff <= base_wp->xoff + (int)base_wp->sx) ||
 		    (wp->xoff + (int)wp->sx >= base_wp->xoff &&
-		    wp->xoff + wp->sx <= base_wp->xoff + base_wp->sx)))
+		    wp->xoff + wp->sx <= base_wp->xoff + base_wp->sx))) {
+			log_debug("%s: base %%%u obscured by %%%u "
+			    "(xoff=%u sx=%u vs base xoff=%u sx=%u)", __func__,
+			    base_wp->id, wp->id,
+			    wp->xoff, wp->sx, base_wp->xoff, base_wp->sx);
 			return (1);
 		}
+		}
 	return (0);
 }
 
@@ -2037,7 +2042,12 @@ screen_write_collect_flush(struct screen_write_ctx *ctx, int scroll_only,
 		ttyctx.num = ctx->scrolled;
 		ttyctx.bg = ctx->bg;
 		ttyctx.obscured = screen_write_pane_obscured(wp);
+		log_debug("%s: obscured=%d for pane %%%u", __func__,
+		    ttyctx.obscured, wp != NULL ? wp->id : 0);
 		tty_write(tty_cmd_scrollup, &ttyctx);
+		if (wp != NULL)
+			log_debug("%s: after scrollup, PANE_REDRAW=%d for %%%u",
+			    __func__, !!(wp->flags & PANE_REDRAW), wp->id);
 
 		if (wp != NULL)
 			ctx->wp->flags |= PANE_REDRAWSCROLLBAR;
diff --git a/tty.c b/tty.c
index 58b294b5..ab3d822f 100644
--- a/tty.c
+++ b/tty.c
@@ -1095,12 +1095,17 @@ tty_redraw_region(struct tty *tty, const struct tty_ctx *ctx)
 	 * If region is large, schedule a redraw. In most cases this is likely
 	 * to be followed by some more scrolling.
 	 */
+	log_debug("%s: %s orlower=%u orupper=%u sy=%u large=%d", __func__,
+	    c->name, ctx->orlower, ctx->orupper, ctx->sy,
+	    tty_large_region(tty, ctx));
 	if (tty_large_region(tty, ctx)) {
 		log_debug("%s: %s large redraw", __func__, c->name);
 		ctx->redraw_cb(ctx);
 		return;
 	}
 
+	log_debug("%s: %s small redraw, drawing rows %u-%u", __func__,
+	    c->name, ctx->orupper, ctx->orlower);
 	for (i = ctx->orupper; i <= ctx->orlower; i++)
 		tty_draw_pane(tty, ctx, i);
 }
@@ -1314,9 +1319,9 @@ tty_clear_area(struct tty *tty, const struct tty_ctx *ctx, u_int py,
 	TAILQ_FOREACH(wpl, &w->z_index, zentry) {
 		if (wpl == wp || ~wpl->flags & PANE_FLOATING)
 			continue;
-		if (wpl->xoff - 1 > (int)(px + nx) || wpl->xoff + wpl->sx + 1 < px)
+		if ((int)wpl->xoff - 1 > (int)(px + nx) || wpl->xoff + wpl->sx + 1 < px)
 			continue;
-		if (wpl->yoff - 1 > (int)(py + ny) || wpl->yoff + wpl->sy + 1 < py)
+		if ((int)wpl->yoff - 1 > (int)(py + ny) || wpl->yoff + wpl->sy + 1 < py)
 			continue;
 		overlap++;
 		if (overlap > 0) break;