Cannot get [password_quality] to work with 7.5.0 on Debian buster

I have a newly-built Debian buster server. I have installed the heimdal 
packages that are available in the buster distribution (currently, these 
all have version number 7.5.0+dfsg-2).

I have this in /etc/krb5.conf:

[password_quality]
     policies           = minimum-length
     min_length         = 10

When I change the password for a user to one that is one-character long, 
kadmin lets me. Here is the command:

% kadmin -p joeuser passwd -p A janeuser
[email protected]'s Password:
% (no error shown)

How do I configure it so that heimdal respects the [password_quality] 
stanza?

Adam Lewenberg