Message: "Class not loaded: geoPHPClass not loaded: GEOSGeometry"

I've recently begun receiving this error message on the /admin/config page:

Class not loaded: geoPHPClass not loaded: GEOSGeometry

(note the missing space between what appears to be two messages).

I don't know exactly when it appeared, but this is an active development site and I'm sure it was fairly recent. Also, so far I have only seen the message on the configuration page at /admin/config.

My mapping features appear to be working normally, but I don't like unknown messages showing up in my admin UI.

I cannot find any reference to this message anywhere. Any guidance is appreciated.

Thanks!