 Plugin breaks RSS feed

I was just notified that my RSS feed is broken. It seems to be an issue with this plugin. I checked the error logs, and this is what I get. Disabling this plugin seems to fix my feed.

[19-Jan-2021 04:16:38 UTC] PHP Parse error: syntax error, unexpected ‘version’ (T_STRING) in /path/to/wp-content/cache/wpp-cache/example.com/feed/index.html on line 1
