[plt-scheme] Warning from planet on install

Whenever I install a new package with Planet I get some errors on stdout
but they dont seem to be fatal so Im just counting them as warnings.

$ planet -i "schematics" "macro.plt" 1 0
standard-module-name-resolver: collection not found: "mred" in any of:
(#<path:/home/kazzmir/.plt-scheme/301/collects>
#<path:/home/kazzmir/archives/progs/plt/collects>)
setup-plt: Error during Compiling .zos for schemeunit
(/home/kazzmir/.plt-scheme/planet/300/301/cache/schematics/schemeunit.plt/1/2)
setup-plt:   standard-module-name-resolver: collection not found: "mred"
in any of: (#<path:/home/kazzmir/.plt-scheme/301/collects>
#<path:/home/kazzmir/archives/progs/plt/collects>)

This is probably because I install mzscheme from source without mred,
but why is mred necessary for planet, or at least these modules?

Maybe mred itself could be a module in planet so it will just be
automatically installed if some other module wants it?