diff --git a/src/xdisp.c b/src/xdisp.c
index 171c6ccaa02..255851b9213 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -19535,7 +19535,8 @@ redisplay_window (Lisp_Object window, bool just_this_one_p)
   /* Check whether the buffer to be displayed contains long lines.  */
   if (!NILP (Vlong_line_threshold)
       && !current_buffer->long_line_optimizations_p
-      && CHARS_MODIFF - CHARS_UNCHANGED_MODIFIED > 8)
+      && (CHARS_MODIFF - CHARS_UNCHANGED_MODIFIED > 8
+	  || current_buffer->clip_changed))
     {
       ptrdiff_t cur, next, found, max = 0, threshold;
       threshold = XFIXNUM (Vlong_line_threshold);