diff --git a/line.py b/line.py
index ffbbdbcf86..2953d9338d 100644
--- a/line.py
+++ b/line.py
@@ -72,7 +72,9 @@ class Line(ModelSQL, ModelView):
 
     @classmethod
     def __register__(cls, module_name):
-        cursor = Transaction().connection.cursor()
+        transaction = Transaction()
+        cursor = transaction.connection.cursor()
+        update = transaction.connection.cursor()
         table = cls.__table_handler__(module_name)
         sql_table = cls.__table__()
         pool = Pool()
@@ -86,7 +88,7 @@ class Line(ModelSQL, ModelView):
         # Migration from 3.4: new company field
         if created_company:
             # Don't use FROM because SQLite nor MySQL support it.
-            cursor.execute(*sql_table.update(
+            update.execute(*sql_table.update(
                     [sql_table.company], [work.select(work.company,
                             where=work.id == sql_table.work)]))
         # Migration from 3.4: change hours into timedelta duration
@@ -94,9 +96,9 @@ class Line(ModelSQL, ModelView):
             table.drop_constraint('check_move_hours_pos')
             cursor.execute(*sql_table.select(
                     sql_table.id, sql_table.hours))
-            for id_, hours in cursor.fetchall():
+            for id_, hours in cursor:
                 duration = datetime.timedelta(hours=hours)
-                cursor.execute(*sql_table.update(
+                update.execute(*sql_table.update(
                         [sql_table.duration],
                         [duration],
                         where=sql_table.id == id_))
diff --git a/work.py b/work.py
index 082b74574f..15cd484c61 100644
--- a/work.py
+++ b/work.py
@@ -158,7 +158,7 @@ class Work(DeactivableMixin, ModelSQL, ModelView):
             cursor.execute(*query_table.select(table_w.id, Sum(line.duration),
                     where=red_sql & where,
                     group_by=table_w.id))
-            for work_id, duration in cursor.fetchall():
+            for work_id, duration in cursor:
                 # SQLite uses float for SUM
                 if duration and not isinstance(duration, datetime.timedelta):
                     duration = datetime.timedelta(seconds=duration)