I think I'm seeing a slight regression in the behavior of the mouse wheel with xterm-mouse-mode. This is when running in -nw mode, using Windows PuTTY as a client, with ssh into a linux box where the emacs runs. I've verified that it's nothing in my init.el or site-lisp files. I've verified that the bad behavior described below does not happen when running on the same host with a real xterm. The problem seems to have begun with emacs 24.4. I verified with fresh builds from source that it works with 24.3, but not with 24.4 or 24.5. The problem: When I scroll using the mouse wheel, the buffer scrolls as before, but there's also a screen flash, and a complaint in the mini buffer: "M-[ m" is undefined". It seems that emacs is seeing this escape sequence after each movement of the mouse wheel. I have PuTTY set to report xterm mouse events, and I have xterm-mouse-mode turned on in emacs. I can work around this by adding a global-set-key to recognize the escape sequence and ignore it. As yet, I don't know if my workaround breaks anything else. The escape sequence means "Turn off all special character attributes, e.g., blinking, bold, etc.". Here's the workaround I'm using: (global-set-key (kbd "\e [ m") (lambda () (interactive) nil)) Here is the lossage output under various combinations of emacs version and client. I notice that with 24.4 the character \230 is displayed differently than in 24.3, don't know if that relates to the problem. These are all started as emacs -q -nw. After emacs starts up, I enable xterm-mouse-mode, and then do a single scroll down with the mouse wheel: This is emacs 24.3 with the PuTTY client. The bad behavior is not seen in this case. ESC [ > 0 ; 1 3 6 ; 0 c ESC x x t e r m - m o u s e - m o d e RET ESC [ M a \230 % ESC [ M # \230 % C-h l This is emacs 24.3 with the genuine xterm client. The bad behavior is not seen in this case. ESC [ > 0 ; 2 7 8 ; 0 c ESC ] 1 1 ; r g b : 0 0 0 0 / 0 0 0 0 / 0 0 0 0 ESC \ ESC x x t e r m - m o u s e - m o d e RET ESC [ < 6 5 ; 5 0 ; 1 3 M C-h l This is emacs 24.4 with the PuTTY client. The bad behavior is seen in this case. ESC [ > 0 ; 1 3 6 ; 0 c ESC x x t e r m - m o u s e - m o d e RET ESC [ M a  K ESC [ M #  K C-h l This is emacs 24.4 with the genuine xterm client. The bad behavior is not seen in this case. ESC [ > 0 ; 2 7 8 ; 0 c ESC ] 1 1 ; r g b : 0 0 0 0 / 0 0 0 0 / 0 0 0 0 ESC \ ESC x x t e r m - m o u s e - m o d e RET ESC [ < 6 5 ; 9 6 ; 4 2 M C-h l$ Pasted below is the output from M-x report-emacs-bug on the failing version. I have also tried emacs 24.5 and found the same bad behavior with the PuTTY client. In GNU Emacs 24.4.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.10) of 2015-07-30 on moes System Description: Debian GNU/Linux 7.7 (wheezy) Configured using: `configure --with-xpm=no --with-gif=no --with-tiff=no' Important settings: value of $LANG: en_US.UTF-8 locale-coding-system: utf-8-unix Major mode: Fundamental Minor modes in effect: tooltip-mode: t electric-indent-mode: t mouse-wheel-mode: t tool-bar-mode: t menu-bar-mode: t file-name-shadow-mode: t global-font-lock-mode: t auto-composition-mode: t auto-encryption-mode: t auto-compression-mode: t buffer-read-only: t line-number-mode: t transient-mark-mode: t Recent input: ESC [ > 0 ; 1 3 6 ; 0 c ESC x r e p o r t - e m a c s - b u g RET Recent messages: For information about GNU Emacs and the GNU system, type C-h C-a. Load-path shadows: None found. Features: (shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util help-fns mail-prsvr mail-utils xterm time-date tooltip electric uniquify 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 prog-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 nadvice 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 dbusbind gfilenotify dynamic-setting system-font-setting font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs) Memory information: ((conses 16 77501 7411) (symbols 48 17540 0) (miscs 40 70 113) (strings 32 9242 4336) (string-bytes 1 248382) (vectors 16 7099) (vector-slots 8 341403 33128) (floats 8 65 270) (intervals 56 155 0) (buffers 960 12) (heap 1024 7622 527))