-# c plugins (.so files) with the OSX version Python3 was built with.
-# For Python3.4, this is OSX 10.6, but we need Thread Local Support (__thread)
-if 'darwin' in sys.platform and PY3:
+# c plugins (.so files) with the OSX version Python was built with.
+# We need OSX 10.10, the oldest which supports C++ thread_local.
+if 'darwin' in sys.platform: