Create a new error for when a char is needed but event-to-character gives nil lisp/ChangeLog addition: 2015-03-14 Aidan Kehoe <kehoea@parhasard.net> * cmdloop.el (no-character-typed): New error, for those cases when a keystroke is to be treated as a character but has no character equivalent. * cmdloop.el (read-char-1): Use it. * keymap.el (synthesize-keysym): Use it. src/ChangeLog addition: 2015-03-14 Aidan Kehoe <kehoea@parhasard.net> * general-slots.h (Qno_character_typed): New error symbol. * event-stream.c (syms_of_event_stream): Define it. New error, for those cases when a keystroke is to be treated as a character in some context but has no character equivalent. * cmds.c (Fself_insert_command): Use it.

--- a/lisp/keymap.el	Sat Mar 14 01:16:45 2015 +0000
+++ b/lisp/keymap.el	Sat Mar 14 01:40:49 2015 +0000
@@ -512,7 +512,7 @@
 	     (error "Illegal character in keysym: %c" char))
 	    (t
 	     ;; Illegal event.
-	     (error "Event has no character equivalent: %s" event))))
+	     (error 'no-character-typed event))))
     (vector (intern (concat "" (nreverse list))))))
 
 (defun synthesize-unicode-codepoint (ignore-prompt)