Wanted: Trick for granting permissions to users with hyphens

Hello

I like to grant some permissions to the user www-data (default user
for apache under debian)

GRANT SELECT, UPDATE, INSERT, DELETE ON customer TO herbie, www-data;

The statements throws the following error:
ERROR:  parser: parse error at or near "-" at character 64

Seems to me that hyphens are not allowed for user names. But a »createuser
www-data« is working correct an I can access the database with that
user.

I tried to quote the www-data with 'www-data', www\-data with
the same result.

Any hints? I'm using 7.3.2

Thanks and best regards
Herbie

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Herbert Liechti                                  http://www.thinx.ch
The content management company.         Visit http://www.contentx.ch
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~