1 files changed, 9 insertions, 6 deletions

diff --git a/lisp/follow.el b/lisp/follow.el
index 59b8a8a38fd..7af3a049299 100644
--- a/lisp/follow.el
+++ b/lisp/follow.el
@@ -1208,22 +1208,25 @@ should be a member of WINDOWS, starts at position START."
   (setq win (or win (selected-window)))
   (setq start (or start (window-start win)))
   (save-excursion
-    (let ((done nil)
-          win-start
-          res)
+    (let (done win-start res opoint)
       ;; Always calculate what happens when no line is displayed in the first
       ;; window. (The `previous' res is needed below!)
       (goto-char guess)
       (vertical-motion 0 (car windows))
       (setq res (point))
       (while (not done)
+        (setq opoint (point))
         (if (not (= (vertical-motion -1 (car windows)) -1))
             ;; Hit roof!
             (setq done t res (point-min))
           (setq win-start (follow-calc-win-start windows (point) win))
-          (cond ((= win-start start)    ; Perfect match, use this value
-                 (setq done t)
-                 (setq res (point)))
+          (cond ((>= (point) opoint)
+                 ;; In some pathological cases, vertical-motion may
+                 ;; return -1 even though point has not decreased.  In
+                 ;; that case, avoid looping forever.
+                 (setq done t res (point)))
+                ((= win-start start)    ; Perfect match, use this value
+                 (setq done t res (point)))
                 ((< win-start start)    ; Walked to far, use preious result
                  (setq done t))
                 (t                      ; Store result for next iteration