[racket] find-secs error while building 5.3.2

Hello,

I'm trying to upgrade the FreeBSD ports for Racket 5.3.2, and I'm
getting a strange error while running the install target:

raco setup: --- installing collections ---
raco setup: --- post-installing collections ---
raco setup: post-installing: help
raco setup: post-installing: mred
raco setup: post-installing: mzcom
raco setup: post-installing: mzscheme
raco setup: post-installing: racket/gui
raco setup: 
raco setup: error: during Building docs for /1/lib/racket/collects/plot/scribblings/plot.scrbl
raco setup:   find-secs: non-existent date (inputs: 0 0 0 1 5 1970)
*** [install-3m] Error code 1

"/1" is my test install prefix, but it also happens in poudriere
builds. I'm using the standard tarball with no extra patches.

Is anybody able to suggest what might be going on?

-- 
jimmy