Zstyle command completion does not work for some executables

[Silvio Ricardo Cordeiro <silvioricardoc@xxxxxxxxx>]

On an otherwise empty .zshrc:

Some completion specifications work normally:

> zstyle ':completion:*:*killall*:*' command 'echo testing'
> zstyle ':completion:*:*rake*:*' command 'echo testing'
>

While other completion just do *not* work:

> zstyle ':completion:*:*bash*:*' command 'echo testing'
> zstyle ':completion:*:*some_file_in_PATH*:*' command 'echo testing'

zstyle ':completion:*:*inexistent_executable*:*' command 'echo testing'
>

Is there any way to debug this kind of behavior?  I have tried pressing
"^X?", but the output is the same for "killall" and for "bash"...

-- 
Silvio Ricardo Cordeiro