[plt-scheme] Error at the end of `make install` on 4.1.5

Salutations,

It's been a little while since I've used PLT, but I grabbed the source
for 4.1.5 and went to compile it on my OpenBSD 4.5 x86 box.  At the
end of the `make install` step, I get an error:

:
:
setup-plt: --- post-installing collections ---
setup-plt: post-installing: help
setup-plt: post-installing: mred
setup-plt: post-installing: mysterx
setup-plt: post-installing: mzcom
setup-plt: done
setup-plt: 
setup-plt: error: during Building docs for
/opt/plt/lib/plt/collects/web-server/scribblings/web-server.scrbl
setup-plt:   ffi-obj: couldn't get "scheme_start_atomic" from #f
(Unable to resolve symbol)
gmake[1]: *** [install-3m] Error 1

There's also some warning text earlier:

:
:
setup-plt: running: web-server/scribblings/web-server.scrbl
ffi-obj: couldn't get "scheme_start_atomic" from #f (Unable to resolve symbol)
setup-plt: running: web-server/scribblings/tutorial/continue.scrbl
setup-plt: running: xml/xml.scrbl
setup-plt: WARNING: undefined tag in scribblings/guide/guide.scrbl:
setup-plt:  (part ("(lib web-server/scribblings/web-server.scrbl)" "top"))
setup-plt: WARNING: undefined tag in scribblings/more/more.scrbl:
setup-plt:  (part ("(lib web-server/scribblings/web-server.scrbl)" "top"))
setup-plt: WARNING: undefined tag in web-server/scribblings/tutorial/continue.scrbl:
setup-plt:  (mod-path "web-server/insta")
setup-plt:  (mod-path "web-server/servlet-env")
setup-plt:  ((lib "web-server/servlet.ss") response/c)
setup-plt:  ((lib "web-server/servlet.ss") request?)
setup-plt:  ((lib "web-server/servlet.ss") request)
setup-plt:  ((lib "web-server/servlet-env.ss") serve/servlet)
setup-plt:  ((lib "web-server/servlet.ss") send/suspend/dispatch)
setup-plt: rendering: algol60/algol60.scrbl
:
:

Aside from these things I see nothing wrong.  I'm compiling with
--disable-gl (as I'm on one of those platforms that requires linking
against pthreads and I just don't care about OpenGL anyway).  The
previous version, 4.1.4 installs and runs just fine.  Does this error
constitute something that effectively prevents proper use of the PLT
system, or is it just a warning that's manifested as a make error?

Best regards,

-- 
Taylor Christopher Venable
http://real.metasyntax.net:2357/