Warning when defining variables on the command line

[Matt Wallis]

I want to pass the subtitle into lilypond on the command line because it 
is also required by other programmes (e.g. sox needs the subtitle to 
create a tag for the mp3 it creates).

Looking at 
http://lilypond.org/doc/v2.19/Documentation/usage/command_002dline-usage#basic-command-line-options-for-lilypond, 
I see I can use

    lilypond -e '(define-public subtitle "One Two Three")'

and that I need to include in the .ly file:

    #(use-modules (guile-user))

This works, with a header block like this:

    header { subtitle = \subtitle }

But I now get the warning:

    Parsing...WARNING: #f: imported module (guile-user) overrides core 
binding `%module-public-interface'

Should I be concerned? Is it safe to ignore? Can I suppress this warning?

(Question already asked: 
http://lilypond.1069038.n5.nabble.com/use-modules-guile-user-warning-td151534.html, 
but I couldn't find an answer).