diff --git a/trytond/model/modelstorage.py b/trytond/model/modelstorage.py
index f910d5d587..a05b2d3efd 100644
--- a/trytond/model/modelstorage.py
+++ b/trytond/model/modelstorage.py
@@ -592,7 +592,7 @@ class ModelStorage(Model):
                     warn('too_many_relations_found', value, relation)
                     res = None
                 else:
-                    res = '%s,%s' % (relation, str(res[0]))
+                    res = '%s,%s' % (relation, res[0].id)
                 return res
 
             def get_by_id(value):
diff --git a/trytond/tests/test_importdata.py b/trytond/tests/test_importdata.py
index 71b8e96237..776dfa526f 100644
--- a/trytond/tests/test_importdata.py
+++ b/trytond/tests/test_importdata.py
@@ -364,19 +364,34 @@ class ImportDataTestCase(unittest.TestCase):
             self.assertEqual(self.reference.import_data(['reference'],
                 [['test.import_data.reference.selection,Test']]),
                 (1, 0, 0, 0))
+            reference, = self.reference.search([])
+            self.assertEqual(reference.reference.__name__,
+                'test.import_data.reference.selection')
+            transaction.cursor.rollback()
 
             self.assertEqual(self.reference.import_data(['reference:id'],
                 [['test.import_data.reference.selection,'
                     'test.import_data_reference_selection_test']]),
                 (1, 0, 0, 0))
+            reference, = self.reference.search([])
+            self.assertEqual(reference.reference.__name__,
+                'test.import_data.reference.selection')
+            transaction.cursor.rollback()
 
             self.assertEqual(self.reference.import_data(['reference'],
                 [['']]), (1, 0, 0, 0))
+            reference, = self.reference.search([])
+            self.assertEqual(reference.reference, None)
+            transaction.cursor.rollback()
 
             self.assertEqual(self.reference.import_data(['reference'],
                 [['test.import_data.reference.selection,Test'],
                     ['test.import_data.reference.selection,Test']]),
                 (2, 0, 0, 0))
+            for reference in self.reference.search([]):
+                self.assertEqual(reference.reference.__name__,
+                    'test.import_data.reference.selection')
+            transaction.cursor.rollback()
 
             self.assertEqual(self.reference.import_data(['reference'],
                 [['test.import_data.reference.selection,foo']])[0], -1)