diff --git a/mercurial/repair.py b/mercurial/repair.py
--- a/mercurial/repair.py
+++ b/mercurial/repair.py
@@ -130,7 +130,7 @@
     cl = repo.changelog
 
     # TODO handle undo of merge sets
-    if isinstance(nodelist, str):
+    if isinstance(nodelist, bytes):
         nodelist = [nodelist]
     striplist = [cl.rev(node) for node in nodelist]
     striprev = min(striplist)