I've created a pull request with the fix I applied to the Chicken 5 port
of SRFI-143:

  https://github.com/scheme-requests-for-implementation/srfi-143/pull/1

Thank you both for your help.

  --Sergey

On Tue 17 Nov 2020 04:50:28 PM -08, Arthur A. Gleckler wrote:

> On Tue, Nov 17, 2020 at 4:44 PM John Cowan <xxxxxx@ccil.org> wrote:
>
>> The problem is a Chicken-only bug: in the file "srfi-143.scm", which is
>> Chicken-4-specific, the import renames fxmod to fxremainder.  It should
>> rename fxrem to fxremainder, of course.  I don't know why this wasn't
>> caught before.
>>
>> This file should be replaced upstream with the Chicken-5-specific version
>> that imports `(chicken fixnum)` instead of `chicken`.
>>
>>>
> Thanks.  I'll await a pull request or patch.