diff --git a/unittests/test_entity.py b/unittests/test_entity.py
index 3fdc6af43d3a60ed7cfb466298e4b49729203282..258f6dfd65418eb945d3728ca64429ec866ba460 100644
--- a/unittests/test_entity.py
+++ b/unittests/test_entity.py
@@ -25,7 +25,8 @@
 # pylint: disable=missing-docstring
 import unittest
 
-from caosdb import Entity, Property, Record, RecordType, configure_connection
+from caosdb import (INTEGER, Entity, Property, Record, RecordType,
+                    configure_connection)
 from caosdb.connection.mockup import MockUpServerConnection
 
 
@@ -54,7 +55,7 @@ class TestEntity(unittest.TestCase):
     def test_apply_to_ids(self):
         parent = RecordType(id=3456)
         rec = Record(id=23)
-        p = Property(id=23345)
+        p = Property(id=23345, datatype=INTEGER)
         rec.add_parent(parent)
         rec.add_property(p)
 
@@ -62,8 +63,9 @@ class TestEntity(unittest.TestCase):
             return id_ * -1
         rec.apply_to_ids(invert)
 
-        self.assertEqual(parent.id, -3456)
-        self.assertEqual(p.id, -23345)
+        self.assertEqual(invert(3456), -3456)
+        self.assertEqual(rec.parents[0].id, -3456)
+        self.assertEqual(rec.properties[0].id, -23345)
         self.assertEqual(rec.id, -23)
 
     def test_instanciation(self):