--- a/setuptools/dist.py
+++ b/setuptools/dist.py
@@ -195,7 +195,7 @@ def write_pkg_file(self, file):
             self.long_description_content_type
         )
     if self.provides_extras:
-        for extra in self.provides_extras:
+        for extra in sorted(self.provides_extras):
             write_field('Provides-Extra', extra)