The abbrev--check-chars function in abbrev.el is supposed to check either the current syntax table or the global syntax table. According to the doc string if the second argument is nil the local syntax table is checked, otherwise the global syntax table will be checked. From looking at the code it appears to do the opposite. This means that when asked to check the local syntax table it actually checks the global syntax table. I discovered this when I tried to define an abbrev for "#i" to expand to "#include" but it failed even after I had run (modify-syntax-entry ?# "w"). I have modified the abbrev--check-chars function as below and it now works as I think it is supposed to: (eval-after-load 'abbrev '(defun abbrev--check-chars (abbrev global) "GRC modified: Check if the characters in ABBREV have word syntax in either the current (if global is nil) or standard syntax table." (with-syntax-table (cond ((null global) (syntax-table)) ; these 2 lines have been changed (t (standard-syntax-table))) ; to make this function work as expected (when (string-match "\\W" abbrev) (let ((badchars ()) (pos 0)) (while (string-match "\\W" abbrev pos) (cl-pushnew (aref abbrev (match-beginning 0)) badchars) (setq pos (1+ pos))) (error "Some abbrev characters (%s) are not word constituents %s" (apply 'string (nreverse badchars)) (if global "in the standard syntax" "in this mode"))))))) I am not subscribed to this mailing list so please email me directly if you require any further information. -- Glenn In GNU Emacs 24.3.1 (x86_64-unknown-linux-gnu, X toolkit, Xaw3d scroll bars) of 2013-07-08 on desk137 Windowing system distributor `The Cygwin/X Project', version 11.0.11200000 System Description: CentOS release 4.8 (Final) Configured using: `configure '--program-prefix=g' '--prefix=/vl/edatools/intern/emacs/24.3.nicegui/linux/' '--enable-locallisppath=/vl/edatools/intern/emacs/24.3.nicegui/site-lisp/' '--without-pop' '--with-x-toolkit=lucid' '--without-xpm' '--without-sound' '--without-jpeg' '--without-tiff' '--without-gif' '--without-png' '--without-rsvg' '--without-imagemagick' '--without-selinux'' Important settings: value of $LC_ALL: C value of $LANG: C locale-coding-system: nil default enable-multibyte-characters: t Major mode: Emacs-Lisp Minor modes in effect: which-function-mode: t show-paren-mode: t desktop-save-mode: t tooltip-mode: t mouse-wheel-mode: t menu-bar-mode: t file-name-shadow-mode: t global-font-lock-mode: t font-lock-mode: t auto-composition-mode: t auto-encryption-mode: t auto-compression-mode: t column-number-mode: t line-number-mode: t transient-mark-mode: t Recent input: C-l C-x C-s C-a C-x b c o m m SPC h SPC M-x t o g g SPC r e SPC # i SPC C-/ C-/ C-/ C-/ C-x k C-x b C-x k C-x b a b b SPC C-f C-g C-x C-f C-g M-x r e p o SPC r SPC Recent messages: Loading /user/grc/.xemacs/ctypes...done Saving file /user/grc/.emacs.d/init.el... Wrote /user/grc/.emacs.d/init.el Read-Only mode disabled Undo! [3 times] user-error: No further undo information Mark set [2 times] call-interactively: End of buffer Quit [2 times] Making completion list... Load-path shadows: /vl/edatools/intern/emacs/24.3.nicegui/site-lisp/verilog-mode hides /vl/edatools/intern/emacs/24.3.nicegui/linux/share/emacs/24.3/lisp/progmodes/verilog-mode /vl/edatools/intern/emacs/24.3.nicegui/site-lisp/vhdl-mode hides /vl/edatools/intern/emacs/24.3.nicegui/linux/share/emacs/24.3/lisp/progmodes/vhdl-mode Features: (shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils help-mode add-log ruby-mode perl-mode sh-script smie executable jka-compr edmacro kmacro which-func ctypes cl-macs gv saveplace paren desktop cus-start cus-load mouse-copy frame-restore imenu cmake-mode p4 vc vc-dispatcher show-proto uniquify advice help-fns advice-preload cc-langs cc-mode cc-fonts easymenu cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs alist cl cl-lib grc-funcs time-date tooltip ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar dnd fontset image regexp-opt fringe tabulated-list newcomment lisp-mode register page menu-bar rfn-eshadow timer select scroll-bar 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 minibuffer loaddefs button faces cus-face macroexp files text-properties overlay sha1 md5 base64 format env code-pages mule custom widget hashtable-print-readable backquote make-network-process dynamic-setting font-render-setting x-toolkit x multi-tty emacs)