diff --git a/Lib/posixpath.py b/Lib/posixpath.py
index e9f4251..37da71e 100644
--- a/Lib/posixpath.py
+++ b/Lib/posixpath.py
@@ -427,7 +427,7 @@
             path = normpath(resolved)
     return path
 
-supports_unicode_filenames = False
+supports_unicode_filenames = (sys.platform == 'darwin')
 
 def relpath(path, start=None):
     """Return a relative version of a path"""