diff --git a/swh/storage/bundle.py b/swh/storage/bundle.py
index 5ba6fe21..8d0ccbc3 100644
--- a/swh/storage/bundle.py
+++ b/swh/storage/bundle.py
@@ -1,70 +1,71 @@
 # Copyright (C) 2015  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 
 import tempfile
 
 from .db import Db
 from .objstorage import ObjStorage
 
 TMP_CONTENT_TABLE = 'tmp_content'
 
 
 class Storage():
     """SWH storage proxy, encompassing DB and object storage
 
     """
 
-    def __init__(self, db_connstring, obj_root):
+    def __init__(self, db_conn, obj_root):
         """
         Args:
-            db_connstring: libpq connection string to reach the SWH db
+            db_conn: either a libpq connection string, or an already
+                established psycopg2 connection to the SWH DB
             obj_root: path to the root of the object storage
 
         """
-        self.db = Db(db_connstring)
+        self.db = Db(db_conn)
         self.objstorage = ObjStorage(obj_root)
 
     def add_content(self, content):
         """Add content blobs to the storage
 
         Note: in case of DB errors, objects might have already been added to
         the object storage and will not be removed. Since addition to the
         object storage is idempotent, that should not be a problem.
 
         Args:
             content: iterable of dictionaries representing individual pieces of
                 content to add. Each dictionary has the following keys:
                 - data (bytes): the actual content
                 - one key for each checksum algorithm in
                   swh.core.hashutil(ALGORITHMS), mapped to the corresponding
                   checksum
 
         """
         with self.db.cursor() as c:
             # create temporary table for metadata injection
             c.execute('SELECT swh_content_mktemp()')
 
             with tempfile.TemporaryFile('w+') as f:
                 # prepare tempfile for metadata COPY + add content data to
                 # object storage
                 for cont in content:
                     cont['length'] = len(cont['data'])
                     line = '\t'.join([cont['sha1'], cont['sha1_git'],
                                       cont['sha256'], str(len(cont['data']))])\
                         + '\n'
                     f.write(line)
                     self.objstorage.add_bytes(cont['data'],
                                               obj_id=cont['sha1'])
 
                 # COPY metadata to temporary table
                 f.seek(0)
                 c.copy_from(f, TMP_CONTENT_TABLE,
                             columns=('sha1', 'sha1_git', 'sha256', 'length'))
 
             # move metadata in place and save
             c.execute('SELECT swh_content_add()')
 
         self.db.commit()
diff --git a/swh/storage/db.py b/swh/storage/db.py
index 31f85a04..fcac5662 100644
--- a/swh/storage/db.py
+++ b/swh/storage/db.py
@@ -1,29 +1,33 @@
 # Copyright (C) 2015  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import psycopg2
 
 
 class Db:
     """DB proxy
 
     """
 
-    def __init__(self, connstring):
+    def __init__(self, conn):
         """create a DB proxy, connecting to the DB
 
         Args:
-            connstring: libpq connection string
+            conn: either a libpq connection string, or an established psycopg2
+                connection to the SWH DB
         """
-        self.conn = psycopg2.connect(connstring)
+        if isinstance(conn, psycopg2.extensions.connection):
+            self.conn = conn
+        else:
+            self.conn = psycopg2.connect(conn)
 
     def cursor(self):
         return self.conn.cursor()
 
     def commit(self):
         return self.conn.commit()
 
     def rollback(self):
         return self.conn.rollback()