Hi, I have been using mark-sexp often because I am working with Common Lisp. Until now, the binding C-M-SPC has worked out pretty well. For some reason that I do not understand, the binding has changed. Now, emacs says mark-sexp is bounded to C-M-@ (which does not really work using the keyboard, by the way). This is my humble config file . I am not sure why this has happened. As you see, I have not touched on this specific point. I can only use mark-sexp with the `M-x mark-sexp` which is not very handy. I wish the keybinding worked out. Is this some side-effect from another modification? Why did this happen? And how can I fix it? ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; Recipe using "emacs -Q" 1 - Create an emacs lisp file, could be .emacs; 2 - Insert any valid s-expression, could be (load (expand-file-name "~/.quicklisp/slime-helper.el")) 3 - Put the cursor -!- in the beginning of the s-expression -!-(load (expand-file-name "~/.quicklisp/slime-helper.el")) 4 - Try using `C-M-SPC` or `C-M-@` to achieve mark-sexp. It does NOT work (and it should work). 5 - Press M-x and execute `mark-sexp` it DOES work. Thus, all the s-expression is selected. ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; Information automatically extracted: In GNU Emacs 26.3 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.14) of 2020-03-26, modified by Debian built on lcy01-amd64-020 Windowing system distributor 'The X.Org Foundation', version 11.0.12011000 System Description: Ubuntu 20.04.2 LTS Recent messages: is undefined is undefined Mark set Saved text until "dhardt") (:li "18 anonymous")))))" Mark set Indenting region...done Undo! Type C-x 1 to delete the help window, C-M-v to scroll help. Configured using: 'configure --build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib --libexecdir=/usr/lib --localstatedir=/var/lib --infodir=/usr/share/info --mandir=/usr/share/man --enable-libsystemd --with-pop=yes --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.3/site-lisp:/usr/share/emacs/site-lisp --with-sound=alsa --without-gconf --with-mailutils --build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib --libexecdir=/usr/lib --localstatedir=/var/lib --infodir=/usr/share/info --mandir=/usr/share/man --enable-libsystemd --with-pop=yes --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.3/site-lisp:/usr/share/emacs/site-lisp --with-sound=alsa --without-gconf --with-mailutils --with-x=yes --with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g -O2 -fdebug-prefix-map=/build/emacs-mEZBk7/emacs-26.3+1=. -fstack-protector-strong -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2' 'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro'' Configured features: XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS GLIB NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM THREADS LIBSYSTEMD LCMS2 Important settings: value of $LC_CTYPE: pt_BR.UTF-8 value of $LC_MONETARY: pt_BR.UTF-8 value of $LC_NUMERIC: pt_BR.UTF-8 value of $LC_TIME: pt_BR.UTF-8 value of $LANG: en_US.UTF-8 value of $XMODIFIERS: @im=ibus locale-coding-system: utf-8-unix Major mode: Lisp Minor modes in effect: shell-dirtrack-mode: t helm--remap-mouse-mode: t async-bytecomp-package-mode: t diff-auto-refine-mode: t paredit-mode: t rainbow-delimiters-mode: t delete-selection-mode: t global-wakatime-mode: t wakatime-mode: t disable-mouse-global-mode: t ido-everywhere: t show-paren-mode: t slime-trace-dialog-minor-mode: t slime-autodoc-mode: t 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