Index: setup.py
--- setup.py.orig
+++ setup.py
@@ -142,7 +142,6 @@ def get_cythonize_options():
             "c_string_type": "str",
             "c_string_encoding": "utf-8",
             "embedsignature": True,
-            "freethreading_compatible": True,
         },
     }
     if os.environ.get("PYPROJ_FULL_COVERAGE"):
