Function coding-system-list is supposed to list all coding-systems. But in 21.2.19, it can not list alias names. For example, (memq 'big5 (coding-system-list)) -> (big5 ...) (memq 'cn-big5 (coding-system-list)) -> nil (find-coding-system 'cn-big5) -> #<coding_system big5> This bug only exists in b19 not in previous versions because b19 uses `define-coding-system-alias' instead of `copy-coding-system'. Here is the patch. 1999-07-31 Shenghuo ZHU <zsh(a)cs.rochester.edu&gt; * file-coding.c (add_coding_system_to_list_mapper): Use key instead of value -> name. -- Shenghuo