diff --git a/jsonmodels/fields.py b/jsonmodels/fields.py
index 722c833..07e8ccf 100644
--- a/jsonmodels/fields.py
+++ b/jsonmodels/fields.py
@@ -187,7 +187,7 @@ class ListField(BaseField):
 
     types = (list,)
 
-    def __init__(self, items_types=None, *args, **kwargs):
+    def __init__(self, items_types, *args, **kwargs):
         """Init.
 
         `ListField` is **always not required**. If you want to control number
diff --git a/tests/test_jsonmodels.py b/tests/test_jsonmodels.py
index ab7aad5..00d5f5f 100644
--- a/tests/test_jsonmodels.py
+++ b/tests/test_jsonmodels.py
@@ -3,16 +3,18 @@
 from jsonmodels import models, fields, errors
 
 
-def test_model1():
+class Person(models.Base):
 
-    class Person(models.Base):
+    name = fields.StringField()
+    surname = fields.StringField()
+    age = fields.IntField()
+    cash = fields.FloatField()
+    children = fields.ListField(["Person"])
 
-        name = fields.StringField()
-        surname = fields.StringField()
-        age = fields.IntField()
 
-    alan = Person()
+def test_model1():
 
+    alan = Person()
     alan.name = 'Alan'
     alan.surname = 'Wake'
     alan.age = 34
@@ -20,39 +22,30 @@ class Person(models.Base):
 
 def test_required():
 
-    class Person(models.Base):
-
-        name = fields.StringField(required=True)
-        surname = fields.StringField()
-        age = fields.IntField()
+    class Foo(models.Base):
+        bar = fields.StringField(required=True)
 
-    alan = Person()
+    alan = Foo()
     with pytest.raises(errors.ValidationError):
         alan.validate()
 
-    alan.name = 'Chuck'
+    alan.bar = 'Chuck'
     alan.validate()
 
 
 def test_type_validation():
 
-    class Person(models.Base):
-
-        name = fields.StringField()
-        age = fields.IntField()
-
     alan = Person()
-
     alan.age = 42
 
 
 def test_base_field_should_not_be_usable():
 
-    class Person(models.Base):
+    class Foo(models.Base):
 
         name = fields.BaseField()
 
-    alan = Person()
+    alan = Foo()
 
     with pytest.raises(errors.ValidationError):
         alan.name = 'some name'
@@ -63,13 +56,6 @@ class Person(models.Base):
 
 def test_value_replacements():
 
-    class Person(models.Base):
-
-        name = fields.StringField()
-        age = fields.IntField()
-        cash = fields.FloatField()
-        children = fields.ListField()
-
     alan = Person()
     assert alan.name is None
     assert alan.age is None
@@ -81,7 +67,7 @@ def test_list_field():
 
     class Car(models.Base):
 
-        wheels = fields.ListField()
+        wheels = fields.ListField([str])
 
     viper = Car()
 
@@ -167,9 +153,12 @@ class Garage2(models.Base):
 
 def test_list_validation():
 
+    class Car(models.Base):
+        pass
+
     class Garage(models.Base):
 
-        cars = fields.ListField()
+        cars = fields.ListField([Car])
 
     garage = Garage()
 
@@ -401,25 +390,22 @@ class Person2(object):
 
 def test_items_types():
 
-    class Person(object):
+    class Foo(object):
         pass
 
-    class Person2(object):
+    class Bar(object):
         pass
 
-    allowed_types = (Person,)
+    allowed_types = (Foo,)
 
     field = fields.ListField(allowed_types)
     assert allowed_types == field.items_types
 
-    allowed_types = (Person, Person2)
+    allowed_types = (Foo, Bar)
 
     field = fields.ListField(allowed_types)
     assert allowed_types == field.items_types
 
-    field = fields.ListField()
-    assert tuple() == field.items_types
-
 
 def test_required_embedded_field():
 
diff --git a/tests/test_validation.py b/tests/test_validation.py
index e22c81f..7403048 100644
--- a/tests/test_validation.py
+++ b/tests/test_validation.py
@@ -53,23 +53,18 @@ class Person(models.Base):
     assert 33 == arg.pop()
 
 
-def test_validators_are_always_iterable():
+class Person(models.Base):
+    children = fields.ListField(["Person"])
 
-    class Person(models.Base):
 
-        children = fields.ListField()
+def test_validators_are_always_iterable():
 
     alan = Person()
-
     assert isinstance(alan.get_field('children').validators, list)
 
 
 def test_get_field_not_found():
 
-    class Person(models.Base):
-
-        children = fields.ListField()
-
     alan = Person()
 
     with pytest.raises(errors.FieldNotFound):