Hi Folks, Sorry I cannot send e-mail from Emacs but I have tried to adhere to the message it generated as best as I could. Please describe exactly what actions triggered the bug and the precise symptoms of the bug. If you can, give a recipe starting from `emacs -Q': 1) Load the attached text file (bug-in-gnu-emacs.txt) 2) Mark a region consisting of the first two lines, namely | a | | a 3) Observe that these two lines contain *three* vertical bars 4) Run the command "ESC-x fill-region" 5) Observe that thare are only *two* vertical bars now! I also tested this in a much more recent Emacs build: GNU Emacs 24.4.1 (x86_64-pc-linux-gnu, GTK+ Version 3.14.5) of 2015-03-07 on trouble, modified by Debian In GNU Emacs 23.4.1 (i686-pc-linux-gnu, GTK+ Version 2.24.21) of 2013-10-25 on akateko, modified by Debian Windowing system distributor `The X.Org Foundation', version 11.0.11501000 configured using `configure '--build' 'i686-linux-gnu' '--build' 'i686-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib' '--localstatedir=/var/lib' '--infodir=/usr/share/info' '--mandir=/usr/share/man' '--with-pop=yes' '--enable-locallisppath=/etc/emacs23:/etc/emacs:/usr/local/share/emacs/23.4/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.4/site-lisp:/usr/share/emacs/site-lisp' '--with-crt-dir=/usr/lib/i386-linux-gnu' '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 'build_alias=i686-linux-gnu' 'CFLAGS=-g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Wall -DDEBIAN -O2' 'CPPFLAGS=-D_FORTIFY_SOURCE=2'' Important settings: value of $LC_ALL: value of $LC_COLLATE: C value of $LC_CTYPE: en_US.utf8 value of $LC_MESSAGES: en_US.utf8 value of $LC_MONETARY: en_US.utf8 value of $LC_NUMERIC: en_US.utf8 value of $LC_TIME: en_US.utf8 value of $LANG: en_US.utf8 value of $XMODIFIERS: @im=ibus locale-coding-system: utf-8-unix default enable-multibyte-characters: t Major mode: Text Minor modes in effect: display-time-mode: t shell-dirtrack-mode: t tooltip-mode: t mouse-wheel-mode: t file-name-shadow-mode: t global-font-lock-mode: t font-lock-mode: t blink-cursor-mode: t auto-encryption-mode: t auto-compression-mode: t column-number-mode: t line-number-mode: t Load-path shadows: /usr/share/emacs/23.4/site-lisp/debian-startup hides /usr/share/emacs/site-lisp/debian-startup /usr/share/emacs23/site-lisp/flim/sha1 hides /usr/share/emacs/23.4/lisp/sha1 /usr/share/emacs23/site-lisp/flim/hex-util hides /usr/share/emacs/23.4/lisp/hex-util /usr/share/emacs23/site-lisp/flim/md4 hides /usr/share/emacs/23.4/lisp/md4 /usr/share/emacs23/site-lisp/dictionaries-common/flyspell hides /usr/share/emacs/23.4/lisp/textmodes/flyspell /usr/share/emacs23/site-lisp/dictionaries-common/ispell hides /usr/share/emacs/23.4/lisp/textmodes/ispell /usr/share/emacs23/site-lisp/flim/hmac-md5 hides /usr/share/emacs/23.4/lisp/net/hmac-md5 /usr/share/emacs23/site-lisp/flim/sasl-ntlm hides /usr/share/emacs/23.4/lisp/net/sasl-ntlm /usr/share/emacs23/site-lisp/flim/hmac-def hides /usr/share/emacs/23.4/lisp/net/hmac-def /usr/share/emacs23/site-lisp/flim/sasl-digest hides /usr/share/emacs/23.4/lisp/net/sasl-digest /usr/share/emacs23/site-lisp/flim/ntlm hides /usr/share/emacs/23.4/lisp/net/ntlm /usr/share/emacs23/site-lisp/flim/sasl-cram hides /usr/share/emacs/23.4/lisp/net/sasl-cram /usr/share/emacs23/site-lisp/flim/sasl hides /usr/share/emacs/23.4/lisp/net/sasl /usr/share/emacs23/site-lisp/wl/rfc2368 hides /usr/share/emacs/23.4/lisp/mail/rfc2368 /usr/share/emacs23/site-lisp/latex-cjk-thai/thai-word hides /usr/share/emacs/23.4/lisp/language/thai-word Features: (shadow sort mail-extr message sendmail ecomplete rfc822 mml mml-sec password-cache mm-decode mm-bodies mm-encode mailcap mail-parse rfc2231 rfc2047 rfc2045 qp ietf-drums mailabbrev nnheader gnus-util netrc time-date mm-util mail-prsvr gmm-utils mailheader canlock sha1 sha1-el hex-util hashcash mail-utils emacsbug debug etags latexenc dired-x face-remap cc-awk cc-mode cc-fonts cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs dired-aux tabify man assoc help-fns newcomment tex-mode compile descr-text skeleton help-mode view multi-isearch dabbrev ansi-color compare-w sh-script executable easy-mmode time cus-edit easymenu cus-start cus-load wid-edit iso-transl cl cl-19 edmacro kmacro shell comint ring dired regexp-opt tooltip ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd font-setting tool-bar dnd fontset image fringe lisp-mode register page menu-bar rfn-eshadow timer select scroll-bar mldrag mouse jit-lock font-lock syntax facemenu font-core frame cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean japanese hebrew greek romanian slovak czech european ethiopic indian cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev loaddefs button minibuffer faces cus-face files text-properties overlay md5 base64 format env code-pages mule custom widget hashtable-print-readable backquote make-network-process dbusbind system-font-setting font-render-setting gtk x-toolkit x multi-tty emacs)