diff --git a/hgext/convert/common.py b/hgext/convert/common.py
--- a/hgext/convert/common.py
+++ b/hgext/convert/common.py
@@ -117,7 +117,8 @@ class converter_sink(object):
     def __init__(self, ui, path):
         """Initialize conversion sink (or raise NoRepo("message")
         exception if path is not a valid repository)"""
-        raise NotImplementedError()
+        self.path = path
+        self.ui = ui
 
     def getheads(self):
         """Return a list of this repository's heads"""
diff --git a/hgext/convert/hg.py b/hgext/convert/hg.py
--- a/hgext/convert/hg.py
+++ b/hgext/convert/hg.py
@@ -16,8 +16,7 @@ from common import NoRepo, commit, conve
 
 class mercurial_sink(converter_sink):
     def __init__(self, ui, path):
-        self.path = path
-        self.ui = ui
+        converter_sink.__init__(self, ui, path)
         self.branchnames = ui.configbool('convert', 'hg.usebranchnames', True)
         self.clonebranches = ui.configbool('convert', 'hg.clonebranches', False)
         self.tagsbranch = ui.config('convert', 'hg.tagsbranch', 'default')