exclude_file ignored when exclude is used

Binary package hint: rsnapshot

System: Ubuntu Karmic 9.10
Version: 1.3.0-2

Environment
-----------
I have an exclude file that contains a list of file types that I want to
exclude from backup. For one of my backup paths, I also list a subdirectory
to exclude.

Here are the relevant parts of my rsnapshot.conf:
exclude_file /etc/rsnapshot/exclude
backup /home/myuser mylaptop/ exclude=NoBak
backup /home/otheruser mylaptop/

Here is the relevant line from the exclude file:
/**/*.vdi

Expected Behavior
-----------------
I would expect .vdi files to be excluded from all backup paths, and the
NoBak
directory to be excluded in /home/myuser.

Observed Behavior
-----------------
Though the NoBak subdirectory in /home/myuser is excluded from the backup,
.vdi files are being included. However, .vdi files in /home/otheruser are
not being included.

Other Information
-----------------
rsync behaves appropriately when it is handed both a --exclude and
--exclude-from flag.

I quickly went through the exclude and exclude_file areas of the rsnapshot
Perl script, and the error was not obvious to me. It seemed like the rsync
command line was being built correctly with the ".=" operator.