diff --git a/screen-write.c b/screen-write.c
index 5a2a3882..59b8b027 100644
--- a/screen-write.c
+++ b/screen-write.c
@@ -553,7 +553,7 @@ screen_write_scrollregion(
 		rupper = screen_size_y(s) - 1;
 	if (rlower > screen_size_y(s) - 1)
 		rlower = screen_size_y(s) - 1;
-	if (rupper > rlower)
+	if (rupper >= rlower)	/* cannot be one line */
 		return;
 
 	/* Cursor moves to top-left. */