diff --git a/mercurial/posix.py b/mercurial/posix.py
--- a/mercurial/posix.py
+++ b/mercurial/posix.py
@@ -338,3 +338,5 @@ def unlinkpath(f):
     except OSError:
         pass
 
+def lookupreg(key, name=None, scope=None):
+    return None
diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -475,9 +475,6 @@ def checkwinfilename(path):
             return _("filename ends with '%s', which is not allowed "
                      "on Windows") % t
 
-def lookupreg(key, name=None, scope=None):
-    return None
-
 def hidewindow():
     """Hide current shell window.