Changed the historical-connection implementation to always use new instances.

src/ZODB/Connection.py

@@ -103,10 +103,9 @@ class Connection(ExportImport, object):
         # Multi-database support
         self.connections = {self._db.database_name: self}
 
-        if before:
-            storage = HistoricalStorageAdapter(db.storage, before)
-        else:
         storage = db._mvcc_storage.new_instance()
+        if before:
+            storage = HistoricalStorageAdapter(storage, before)
 
         self._normal_storage = self._storage = storage
         self.new_oid = db.new_oid

src/ZODB/mvccadapter.py

@@ -97,6 +97,7 @@ class MVCCAdapterInstance(Base):
     _copy_methods = Base._copy_methods + (
         'loadSerial', 'new_oid', 'tpc_vote',
         'checkCurrentSerialInTransaction', 'tpc_abort',
+        'loadBefore',
         )
 
     def __init__(self, base):