diff --git a/example_app/models.py b/example_app/models.py
index 7ec0f806..7eafe4d1 100644
--- a/example_app/models.py
+++ b/example_app/models.py
@@ -34,9 +34,9 @@ class AllFieldsModel(db.Document):
     file_field = db.FileField()
     float_field = db.FloatField()
     int_field = db.IntField()
-    list_field = db.ListField(field=db.StringField)
+    list_field = db.ListField(field=db.StringField())
     reference_field = db.ReferenceField(document_type=Todo)
-    sorted_list_field = db.SortedListField(field=db.StringField)
+    sorted_list_field = db.SortedListField(field=db.StringField())
     string_field = db.StringField()
     url_field = db.URLField()
     cached_reference_field = db.CachedReferenceField(document_type=Todo)
diff --git a/tests/test_forms_v2.py b/tests/test_forms_v2.py
index 1884139b..57499407 100644
--- a/tests/test_forms_v2.py
+++ b/tests/test_forms_v2.py
@@ -87,9 +87,9 @@ class AllFieldsModel(db.Document):
         file_field = db.FileField()
         float_field = db.FloatField()
         int_field = db.IntField()
-        list_field = db.ListField(field=db.StringField)
+        list_field = db.ListField(field=db.StringField())
         reference_field = db.ReferenceField(document_type=Todo)
-        sorted_list_field = db.SortedListField(field=db.StringField)
+        sorted_list_field = db.SortedListField(field=db.StringField())
         string_field = db.StringField()
         url_field = db.URLField()
         cached_reference_field = db.CachedReferenceField(document_type=Todo)