diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -237,7 +237,6 @@ def parents(repo, subset, x):
     """``parents([set])``
     The set of all parents for all changesets in set, or the working directory.
     """
-    repo.ui.debug(repr(x), '\n')
     if x is None:
         ps = tuple(p.rev() for p in repo[x].parents())
         return [r for r in subset if r in ps]
diff --git a/tests/test-revset-dirstate-parents.t b/tests/test-revset-dirstate-parents.t
--- a/tests/test-revset-dirstate-parents.t
+++ b/tests/test-revset-dirstate-parents.t
@@ -18,7 +18,6 @@
   ('func', ('symbol', 'p2'), None)
   $ try 'parents()'
   ('func', ('symbol', 'parents'), None)
-  None
 
 null revision
   $ log 'p1()'