su(1) suspends the process

For some time (roughly a year), -current has had a problem that
invoking su(1) sometimes suspends the caller.  I thought this had been
fixed but it still (or again) occurs in a fresh (2 day old)
-current/amd64.

Scenario: I'm building a port (OOo so there are lots of dependencies
along the way) inside a script (in case it blows up) and am fairly
consistently getting the following on each 'make install':

===>  Checking if archivers/p5-IO-Compress-Zlib already installed
===>  Switching to root credentials for 'install' target
zsh: suspended (tty output)  make
turion% fg
[1]  + continued  make
Password:
Installing /usr/local/lib/perl5/site_perl/5.8.8/IO/Compress/Deflate.pm

This is somewhat of a PITA.  (Yes, I'm using zsh but it's built using
an up-to-date ports tree on the current OS).

-- 
Peter Jeremy