diff --git a/rero_ils/modules/acquisition/acq_orders/api.py b/rero_ils/modules/acquisition/acq_orders/api.py
index 629a70cc8d..ebc9017003 100644
--- a/rero_ils/modules/acquisition/acq_orders/api.py
+++ b/rero_ils/modules/acquisition/acq_orders/api.py
@@ -350,16 +350,22 @@ def get_order_lines(self, output=None, includes=None):
         :param includes: a list of statuses to include order lines.
         :return a generator of related order lines (or length).
         """
-        query = AcqOrderLinesSearch().filter('term', acq_order__pid=self.pid)
+        query = AcqOrderLinesSearch()\
+            .filter('term', acq_order__pid=self.pid)
         if includes:
             query = query.filter('terms', status=includes)
 
         if output == 'count':
             return query.count()
         elif output == 'query':
-            return query
+            return query \
+                .params(preserve_order=True) \
+                .sort({'pid': {"order": "asc"}})
         else:
-            return get_objects(AcqOrderLine, query)
+            return get_objects(AcqOrderLine, query
+                               .params(preserve_order=True)
+                               .sort({'pid': {"order": "asc"}})
+                               )
 
     def get_order_provisional_total_amount(self):
         """Get provisional total amount of this order."""