diff --git a/session_redis/README.rst b/session_redis/README.rst
index 949f8b4..e4e32ec 100644
--- a/session_redis/README.rst
+++ b/session_redis/README.rst
@@ -18,6 +18,10 @@ The storage of sessions in Redis is activated using environment variables.
   the sessions (default is 7 days)
 * ``ODOO_SESSION_REDIS_EXPIRATION_ANONYMOUS`` is the time in seconds before expiration of
   the anonymous sessions (default is 3 hours)
+* ``ODOO_SESSION_REDIS_COPY_EXISTING_FS_SESSIONS`` when ``1`` or ``true`` copies the existing odoo sessions from
+  the filesystem to redis when starting
+* ``ODOO_SESSION_REDIS_PURGE_EXISTING_FS_SESSIONS`` when ``1`` or ``true`` deletes the existing odoo sessions from
+  the filesystem to redis when starting
 
 
 The keys are set to ``session:<session id>``.
@@ -32,8 +36,12 @@ Limitations
 
 * The server has to be restarted in order for the sessions to be stored in
   Redis.
-* All the users will have to login again as their previous session will be
-  dropped.
 * The addon monkey-patch ``odoo.http.Root.session_store`` with a custom
   method when the Redis mode is active, so incompatibilities with other addons
   is possible if they do the same.
+
+Preseve Sessions
+----------------
+
+In order to preserve sessions when switching to redis run odoo with
+``ODOO_SESSION_REDIS_COPY_EXISTING_FS_SESSIONS=true odoo --load session_redis --stop-after-init``
diff --git a/session_redis/http.py b/session_redis/http.py
index a4b5c17..57eed19 100644
--- a/session_redis/http.py
+++ b/session_redis/http.py
@@ -77,6 +77,20 @@ def purge_fs_sessions(path):
             pass
 
 
+def copy_fs_sessions(path):
+    from odoo.http import OpenERPSession
+    import werkzeug.contrib.sessions
+    werkzeug_session_store = werkzeug.contrib.sessions.FilesystemSessionStore(path, session_class=OpenERPSession)
+    session_store = http.Root().session_store
+    filename_prefix='werkzeug_'
+    filename_suffix = '.sess'
+
+    for fname in os.listdir(path):
+        path = os.path.join(path, fname)
+        session = werkzeug_session_store.get(fname[len(filename_prefix):len(filename_suffix) * -1])
+        session_store.save(session)
+
+
 if is_true(os.environ.get('ODOO_SESSION_REDIS')):
     if sentinel_host:
         _logger.debug("HTTP sessions stored in Redis with prefix '%s'. "
@@ -88,5 +102,9 @@ if is_true(os.environ.get('ODOO_SESSION_REDIS')):
 
     http.Root.session_store = session_store
     http.session_gc = session_gc
-    # clean the existing sessions on the file system
-    purge_fs_sessions(odoo.tools.config.session_dir)
+
+    if is_true(os.environ.get('ODOO_SESSION_REDIS_COPY_EXISTING_FS_SESSIONS')):
+        copy_fs_sessions(odoo.tools.config.session_dir)
+    if is_true(os.environ.get('ODOO_SESSION_REDIS_PURGE_EXISTING_FS_SESSIONS')):
+        # clean the existing sessions on the file system
+        purge_fs_sessions(odoo.tools.config.session_dir)