lmtpd Internal error: asserstion failed: append.c

[Shelley Waltz]

I am running a postfix-cyrus-amavis configuration.  This is a new setup
and I am testing sending a simple local message.  I receive this error in
attempting
delivery ...

(host domain.edu[/var/lib/imap/socket/lmtp] said: 421 4.3.0 lmtpd:
Internal error: assertion failed: append.c: 479: stage != NULL &&
stage->parts[0] != '\0' (in reply to end of DATA command))

What might cause this?