I reported an issue in the haven GitHub page but I'm seeing that it may be a ReadStat issues. I'm finding that haven/ReadStat is working fine with earlier versions of SPSS but is reporting an error when reading in a .por file created by SPSS v25 -- even a super-simple file. When running directly in ReadStat I also see an issue.

In the attached zip I included both a .sav and a .por of the exact same data created from the most recent version of SPSS and I find that reading the .sav works perfectly while the .por reports an error.

# Works perfectly
readstat -f tiny_spss25_locale.sav sav.csv

# Error
readstat -f tiny_spss25_locale.por por.csv
# Error processing tiny_spss25_locale.por: Invalid file, or file has unsupported features

Any suggestions?

tiny_spss25_locale.zip