diff -r e16ca9fde7aa -r a12a9af7536c mercurial/interfaces/repository.py
--- a/mercurial/interfaces/repository.py	Wed Sep 04 02:43:17 2019 +0200
+++ b/mercurial/interfaces/repository.py	Wed Aug 07 17:55:44 2019 +0200
@@ -35,9 +35,12 @@
 REVISION_FLAG_CENSORED = 1 << 15
 REVISION_FLAG_ELLIPSIS = 1 << 14
 REVISION_FLAG_EXTSTORED = 1 << 13
+REVISION_FLAG_SIDEDATA = 1 << 12
 
 REVISION_FLAGS_KNOWN = (
-    REVISION_FLAG_CENSORED | REVISION_FLAG_ELLIPSIS | REVISION_FLAG_EXTSTORED)
+    REVISION_FLAG_CENSORED | REVISION_FLAG_ELLIPSIS | REVISION_FLAG_EXTSTORED
+    | REVISION_FLAG_SIDEDATA
+)
 
 CG_DELTAMODE_STD = b'default'
 CG_DELTAMODE_PREV = b'previous'