Including spaces in adduser command

[Anand Buddhdev]

I'm busy testing a Portfile in which I have to use the adduser command
to add a user account to the system. My recipe looks like this:

post-destroot {
  addgroup nsd
  adduser nsd gid=nsd shell=/sbin/nologin home=${prefix}/var/db/nsd
realname=NSD User
}

However, when the account is created on the system, its real name is
set to just "NSD". So I tried putting quotes around "NSD User", but
then the real name is set to "NSD. That's right, a single quote,
followed by the words NSD. I also tried it with a backslash before the
space, NSD\ User, but then I get the backspace in the real name.

How can I get adduser to create the account with the string "NSD User"
as the real name? Am I missing something obvious? I'm using Macports
1.710.

Regards,

Anand