diff --git a/cps/db.py b/cps/db.py
index a519d5bf..2cf1d98b 100644
--- a/cps/db.py
+++ b/cps/db.py
@@ -48,6 +48,7 @@ try:
 except ImportError:
     use_unidecode = False
 
+Session = None
 
 cc_exceptions = ['datetime', 'comments', 'composite', 'series']
 cc_classes = {}
@@ -409,6 +410,7 @@ class CalibreDB():
     def setup_db(self, config, app_db_path):
         self.config = config
         self.dispose()
+        global Session
 
         if not config.config_calibre_dir:
             config.invalidate()
@@ -678,6 +680,7 @@ class CalibreDB():
         conn.create_function("title_sort", 1, _title_sort)
 
     def dispose(self):
+        # global session
 
         old_session = self.session
         self.session = None
diff --git a/cps/tasks/convert.py b/cps/tasks/convert.py
index d0b59dc8..2b679fc0 100644
--- a/cps/tasks/convert.py
+++ b/cps/tasks/convert.py
@@ -53,7 +53,7 @@ class TaskConvert(CalibreTask):
 
     def _convert_ebook_format(self):
         error_message = None
-        # local_session = db.Session()
+        local_session = db.Session()
         file_path = self.file_path
         book_id = self.bookid
         format_old_ext = u'.' + self.settings['old_book_format'].lower()
@@ -94,10 +94,10 @@ class TaskConvert(CalibreTask):
                                          book_format=self.settings['new_book_format'].upper(),
                                          book=book_id, uncompressed_size=os.path.getsize(file_path + format_new_ext))
                 try:
-                    calibre_db.session.merge(new_format)
-                    calibre_db.session.commit()
+                    local_session.merge(new_format)
+                    local_session.commit()
                 except SQLAlchemyError as e:
-                    calibre_db.session.rollback()
+                    local_session.rollback()
                     log.error("Database error: %s", e)
                     return
                 self.results['path'] = cur_book.path