(fill-context-prefix): Be stricter about

whether first-line prefix is compatible with second-line prefix.

1 files changed, 5 insertions, 3 deletions

diff --git a/lisp/textmodes/fill.el b/lisp/textmodes/fill.el
index e4ebd2a9030..d73da1105f6 100644
--- a/lisp/textmodes/fill.el
+++ b/lisp/textmodes/fill.el
@@ -210,12 +210,14 @@ act as a paragraph-separator."
           ;; If we get a fill prefix from the second line,
           ;; make sure it or something compatible is on the first line too.
           (and second-line-prefix first-line-prefix
-               (if (or (string-match (regexp-quote second-line-prefix)
+               (if (or (string-match (concat "\\`"
+                                             (regexp-quote second-line-prefix)
+                                             "\\(\\'\\|[ \t]\\)")
                                      first-line-prefix)
-                       (and (string-match "[ \t]" second-line-prefix)
+                       (and (string-match "\\`[ \t]+\\'" second-line-prefix)
                             (>= (string-width first-line-prefix)
                                 (string-width second-line-prefix))))
-                     second-line-prefix))
+                   second-line-prefix))
         ;; If we get a fill prefix from a one-line paragraph,
         ;; maybe change it to whitespace,
         ;; and check that it isn't a paragraph starter.