diff --git a/tests/test_query_select_field.py b/tests/test_query_select_field.py
index e2cc481..8496854 100644
--- a/tests/test_query_select_field.py
+++ b/tests/test_query_select_field.py
@@ -348,6 +348,7 @@ def test_multiple_values_without_query_factory(self):
 
         form = MyForm(DummyPostData(cities=['1', '666']))
         form.cities.query = self.session.query(self.City)
+        assert not form.validate()
         assert [x.id for x in form.cities.data] == [1]
         assert not form.validate()
         form.populate_obj(obj)
diff --git a/wtforms_alchemy/fields.py b/wtforms_alchemy/fields.py
index 362a744..79488c6 100644
--- a/wtforms_alchemy/fields.py
+++ b/wtforms_alchemy/fields.py
@@ -568,7 +568,7 @@ def process_formdata(self, valuelist):
         self._formdata = set(valuelist)
 
     def pre_validate(self, form):
-        if self._invalid_formdata:
+        if self.data and self._invalid_formdata:
             raise ValidationError(self.gettext('Not a valid choice'))
         elif self.data:
             obj_list = list(x[1] for x in self._get_object_list())