I mentioned this on IRC, and Paul is looking into why the change was made. I'm mentioning here in case someone knows the reason. Why was this change made? The library files on mingw64 changed: For geos < 3.11 the files were libgeos.dll, libgeos_c.dll For geos 3.11 (including the just released 3.11.0beta1) libgeos_c-1.dll, libgeos-3.11.0.dll