Path to index-processor with imakeidx

I need to use an older version of xindy for my indexing because of a bug/change in the up-to-date version that comes with texlive. Thus I’d like to specify the path to imakeidx to save me the trouble of compiling manually and avoid the extra runs.

Simply adding the path to the program= option produces a xkeyval Error: value /usr/local/texlive/2016/bin/x86_64-darwin/xindy250 is not allowed
Is there a way/hack to make imakeidx use the my old xindy?