diff --git a/tests/test-revlog-v2.t b/tests/test-revlog-v2.t
--- a/tests/test-revlog-v2.t
+++ b/tests/test-revlog-v2.t
@@ -29,7 +29,7 @@
 Unknown flags to revlog are rejected
 
   >>> with open('.hg/store/00changelog.i', 'wb') as fh:
-  ...     fh.write('\x00\x04\xde\xad')
+  ...     fh.write(b'\x00\x04\xde\xad')
 
   $ hg log
   abort: unknown flags (0x04) in version 57005 revlog 00changelog.i!