--- a/mercurial/upgrade.py	Mon Aug 10 15:47:21 2020 +0530
+++ b/mercurial/upgrade.py	Tue Aug 11 13:43:43 2020 +0530
@@ -64,7 +64,7 @@
         # It should (hopefully) not exist in the wild.
         b'parentdelta',
         # Upgrade should operate on the actual store, not the shared link.
-        b'shared',
+        requirements.SHARED_REQUIREMENT,
     }