diff --git a/lisp/textmodes/fill.el b/lisp/textmodes/fill.el
index 73d76a8ac67..4e161099cd6 100644
--- a/lisp/textmodes/fill.el
+++ b/lisp/textmodes/fill.el
@@ -705,7 +705,10 @@ space does not end a sentence, so don't break a line there."
     (goto-char from-plus-indent))
 
   (if (not (> to (point)))
-      nil ;; There is no paragraph, only whitespace: exit now.
+      ;; There is no paragraph, only whitespace: exit now.
+      (progn
+        (set-marker to nil)
+        nil)
 
     (or justify (setq justify (current-justification)))
 
@@ -791,6 +794,7 @@ space does not end a sentence, so don't break a line there."
       ;; Leave point after final newline.
       (goto-char to)
       (unless (eobp) (forward-char 1))
+      (set-marker to nil)
       ;; Return the fill-prefix we used
       fill-prefix)))