[racket] raco distribute produces non-portable folder

I ran raco distribute on a 64-bit Windows running 32-bit Racket 6.0, 
then moved the resulting folder to another machine. But suddenly this 
error appears in the console windows and the program refuses to run:

file-exists?: contract violation
   expected: path-string?
   given: #f
   context...:
    c:\program files (x86)\racket\collects\racket\file.rkt:393:0: get-prefs
    c:\program files (x86)\racket\collects\racket\file.rkt:510:3
    c:\program files (x86)\racket\collects\racket\file.rkt:492:0: 
get-preference75
    #%embedded:g2619:style: [running body]
    #%embedded:g2596:snip: [traversing imports]
    #%embedded:g2587:contract: [traversing imports]
    #%embedded:g2578:snip: [traversing imports]
    #%embedded:g2129:mred: [traversing imports]
    #%embedded:g2117:mred: [traversing imports]
    #%embedded:g2105:main: [traversing imports]
    #%embedded:g2093:base: [traversing imports]
    #%embedded:g651:gui: [traversing imports]
    #%mzc:main: [traversing imports]
    loop

FYI the thing I'm building is my own project 
<https://github.com/KirisurfProject/kirisurf-racket>, the process is 
basically

raco exe --gui --ico kiri.ico main.rkt
raco distribute WINBUILD/tree main.exe

Thanks a ton!