diff --git a/mercurial/cmd_impls/graft.py b/mercurial/cmd_impls/graft.py
index a48c688d3e809ee7f4cc11319a68f97932a9c5db_bWVyY3VyaWFsL2NtZF9pbXBscy9ncmFmdC5weQ==..1802d9afddf710eb3875b827ce60b87b9ce3cd7d_bWVyY3VyaWFsL2NtZF9pbXBscy9ncmFmdC5weQ== 100644
--- a/mercurial/cmd_impls/graft.py
+++ b/mercurial/cmd_impls/graft.py
@@ -20,7 +20,7 @@
     elif action == "GRAFT":
         return _graft_revisions(ui, repo, graftstate, *args)
     else:
-        raise error.ProgrammingError(b'unknown action: %s' % action)
+        raise error.ProgrammingError('unknown action: %s' % action)
 
 
 def _process_args(ui, repo, *revs, **opts):