Virtualmin / postfix bug

When I go to add an email forward to a virtual server user account (in 'Edit Mail and FTP Users > Mail forwarding settings'), I am getting this error:

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Error - Perl execution failed

Undefined subroutine &postfix::rebuild_map_cmd called at /usr/libexec/webmin/postfix/aliases-lib.pl line 239.
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Status: 
Closed (fixed)