Spaces after Subject prefix

[ISP List]

According to mailscanner.conf, a single space is inserted after the
optional Subject line prefix for positive Virus or Spam matches:

# What text do we want to put on the front (gets followed by a " ")

e.g.

Subject: {SPAM?} This is my subject

However, it appears that in reality two spaces are added:

Subject: {SPAM?}  This is my subject

In the sendmail.pl code, I find where a single space is inserted:

e.g.

       $newheaders = MTA::PrependHeader($newheaders, "Subject:",
                                        $Config::SpamSubjectText, ' ')

I'm curious as to where the "extra" space is coming from.  I've double
checked that in my mailscanner.conf the "Spam Subject Text" line does not
contain a trailing space.

--Mike