--- a/mercurial/utils/repoviewutil.py	Sun Oct 06 09:45:02 2019 -0400
+++ b/mercurial/utils/repoviewutil.py	Sun Oct 06 09:48:39 2019 -0400
@@ -15,10 +15,10 @@
 # This create and ordering used for branchmap purpose.
 # the ordering may be partial
 subsettable = {
-    None: 'visible',
-    'visible-hidden': 'visible',
-    'visible': 'served',
-    'served.hidden': 'served',
-    'served': 'immutable',
-    'immutable': 'base',
+    None: b'visible',
+    b'visible-hidden': b'visible',
+    b'visible': b'served',
+    b'served.hidden': b'served',
+    b'served': b'immutable',
+    b'immutable': b'base',
 }