diff --git a/mercurial/utils/compression.py b/mercurial/utils/compression.py
--- a/mercurial/utils/compression.py
+++ b/mercurial/utils/compression.py
@@ -185,7 +185,7 @@ class compressormanager:
         """
         assert role in (SERVERROLE, CLIENTROLE)
 
-        attr = b'serverpriority' if role == SERVERROLE else b'clientpriority'
+        attr = 'serverpriority' if role == SERVERROLE else 'clientpriority'
 
         engines = [self._engines[e] for e in self._wiretypes.values()]
         if onlyavailable:
diff --git a/mercurial/wireprototypes.py b/mercurial/wireprototypes.py
--- a/mercurial/wireprototypes.py
+++ b/mercurial/wireprototypes.py
@@ -367,9 +367,7 @@ def supportedcompengines(ui, role):
     # No explicit config. Filter out the ones that aren't supposed to be
     # advertised and return default ordering.
     if not configengines:
-        attr = (
-            b'serverpriority' if role == util.SERVERROLE else b'clientpriority'
-        )
+        attr = 'serverpriority' if role == util.SERVERROLE else 'clientpriority'
         return [
             e for e in compengines if getattr(e.wireprotosupport(), attr) > 0
         ]