[dovecot quota-status] error "Invalid character in path"

[k675154 at keit.eu]

Hello,

I'm using using:
- dovecot 2.3.3 (dcead646b)
- postfix 3.3.1
- dovecot "quota = maildir:User quota"

I'm facing the error:

"quota-status: Error: quota-status: Client sent
invalid recipient address: Invalid character in path"

This occurred with this e-mail address:
"John Smith"@keit.eu

Well I know it is not a conventional address but it is normally
perfectly authorized.

When I disable quota check, I can received correctly the incoming
e-mail.

So is there a mean to enable quota check with this kind of e-mail
address ?

Thanks