diff --git a/remotefilelog/basestore.py b/remotefilelog/basestore.py
--- a/remotefilelog/basestore.py
+++ b/remotefilelog/basestore.py
@@ -380,3 +380,12 @@
                   % (removed, count,
                      float(originalsize) / 1024.0 / 1024.0 / 1024.0,
                      float(size) / 1024.0 / 1024.0 / 1024.0))
+
+class baseunionstore(object):
+    def __init__(self, *args, **kwargs):
+        pass
+
+    def markforrefresh(self):
+        for store in self.stores:
+            if util.safehasattr(store, 'markforrefresh'):
+                store.markforrefresh()
diff --git a/remotefilelog/contentstore.py b/remotefilelog/contentstore.py
--- a/remotefilelog/contentstore.py
+++ b/remotefilelog/contentstore.py
@@ -28,8 +28,10 @@
     # The actual delta or full text data.
     DATA = 4
 
-class unioncontentstore(object):
+class unioncontentstore(basestore.baseunionstore):
     def __init__(self, *args, **kwargs):
+        super(unioncontentstore, self).__init__(*args, **kwargs)
+
         self.stores = args
         self.writestore = kwargs.get('writestore')
 
@@ -144,11 +146,6 @@
         for store in self.stores:
             store.markledger(ledger, options)
 
-    def markforrefresh(self):
-        for store in self.stores:
-            if util.safehasattr(store, 'markforrefresh'):
-                store.markforrefresh()
-
 class remotefilelogcontentstore(basestore.basestore):
     def __init__(self, *args, **kwargs):
         super(remotefilelogcontentstore, self).__init__(*args, **kwargs)
diff --git a/remotefilelog/metadatastore.py b/remotefilelog/metadatastore.py
--- a/remotefilelog/metadatastore.py
+++ b/remotefilelog/metadatastore.py
@@ -1,8 +1,10 @@
 import basestore, shallowutil
 from mercurial.node import hex, nullid
 
-class unionmetadatastore(object):
+class unionmetadatastore(basestore.baseunionstore):
     def __init__(self, *args, **kwargs):
+        super(unionmetadatastore, self).__init__(*args, **kwargs)
+
         self.stores = args
         self.writestore = kwargs.get('writestore')