diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -111,7 +111,7 @@ def loglimit(opts):
         limit = None
     return limit
 
-def revsingle(repo, revspec, default=None):
+def revsingle(repo, revspec, default='.'):
     if not revspec:
         return repo[default]