diff --git a/trytond/model/modelstorage.py b/trytond/model/modelstorage.py
index 787aff4d06..aef02cd40c 100644
--- a/trytond/model/modelstorage.py
+++ b/trytond/model/modelstorage.py
@@ -285,7 +285,7 @@ class ModelStorage(Model):
 
                 if field_name in default:
                     data[field_name] = default[field_name]
-                elif (isinstance(cls._fields[field_name], fields.Function)
+                if (isinstance(cls._fields[field_name], fields.Function)
                         and not isinstance(
                             cls._fields[field_name], fields.MultiValue)):
                     del data[field_name]
diff --git a/trytond/tests/test_copy.py b/trytond/tests/test_copy.py
index a4c1636043..35f98d565c 100644
--- a/trytond/tests/test_copy.py
+++ b/trytond/tests/test_copy.py
@@ -44,6 +44,24 @@ class CopyTestCase(unittest.TestCase):
             self.assertEqual([x.name for x in one2many.one2many],
                 [x.name for x in one2many_copy.one2many])
 
+    @with_transaction()
+    def test_one2many_default(self):
+        "Test copy one2many with default"
+        pool = Pool()
+        One2many = pool.get('test.copy.one2many')
+        Target = pool.get('test.copy.one2many.target')
+
+        record = One2many(name="Test")
+        record.save()
+        target = Target(name="Target")
+        target.save()
+
+        record_copy, = One2many.copy(
+            [record], default={'one2many': [target.id]})
+
+        self.assertListEqual(
+            [x.name for x in record_copy.one2many], [target.name])
+
     @with_transaction()
     def test_many2many(self):
         'Test copy many2many'
@@ -74,6 +92,23 @@ class CopyTestCase(unittest.TestCase):
             self.assertEqual([x.name for x in many2many.many2many],
                 [x.name for x in many2many_copy.many2many])
 
+    @with_transaction()
+    def test_many2many_default(self):
+        "Test copy many2many with default"
+        pool = Pool()
+        Many2many = pool.get('test.copy.many2many')
+        Target = pool.get('test.copy.many2many.target')
+
+        record = Many2many(name="Test")
+        record.save()
+        target = Target(name="Target")
+        target.save()
+
+        record_copy, = Many2many.copy(
+            [record], default={'many2many': [target.id]})
+
+        self.assertSequenceEqual(record_copy.many2many, [target])
+
 
 def suite():
     return unittest.TestLoader().loadTestsFromTestCase(CopyTestCase)