diff --git a/docs/orms.rst b/docs/orms.rst
index 3839707..5967e1b 100644
--- a/docs/orms.rst
+++ b/docs/orms.rst
@@ -128,7 +128,11 @@ Extra fields
 
     .. method:: __init__(self, password)
 
-        :param str password: Default password.
+        :param str or None password: Default password.
+
+    .. note:: When the ``password`` argument is ``None``, the resulting password is
+              unusable as if ``set_unusable_password()`` were used. This is distinct
+              from setting the password to an empty string.
 
     .. code-block:: python
 
@@ -149,6 +153,10 @@ Extra fields
         >>> other_user = UserFactory.create(password='other_pw')
         >>> check_password('other_pw', other_user.password)
         True
+        >>> # Set unusable password
+        >>> no_password_user = UserFactory.create(password=None)
+        >>> no_password_user.has_usable_password()
+        False
 
 
 .. class:: FileField
diff --git a/factory/django.py b/factory/django.py
index 87b6fd5..9526b77 100644
--- a/factory/django.py
+++ b/factory/django.py
@@ -311,7 +311,7 @@ class mute_signals:
             logger.debug('mute_signals: Restoring signal handlers %r',
                          receivers)
 
-            signal.receivers += receivers
+            signal.receivers = receivers + signal.receivers
             with signal.lock:
                 # Django uses some caching for its signals.
                 # Since we're bypassing signal.connect and signal.disconnect,

diff --git a/tests/test_django.py b/tests/test_django.py
index 19729e0..066d792 100644
--- a/tests/test_django.py
+++ b/tests/test_django.py
@@ -941,6 +941,22 @@ class PreventSignalsTestCase(django_test.TestCase):
 
         self.assertTrue(self.handlers.created_during_instantiation.called)
 
+    def test_signal_receiver_order_restored_after_mute_signals(self):
+        def must_be_first(*args, **kwargs):
+            self.handlers.do_stuff(1)
+
+        def must_be_second(*args, **kwargs):
+            self.handlers.do_stuff(2)
+
+        signals.post_save.connect(must_be_first)
+        with factory.django.mute_signals(signals.post_save):
+            WithSignalsFactory(post_save_signal_receiver=must_be_second)
+            self.assertEqual(self.handlers.do_stuff.call_args_list, [mock.call(2)])
+
+        self.handlers.reset_mock()
+        WithSignalsFactory(post_save_signal_receiver=must_be_second)
+        self.assertEqual(self.handlers.do_stuff.call_args_list, [mock.call(1), mock.call(2)])
+
     def test_signal_cache(self):
         with factory.django.mute_signals(signals.pre_save, signals.post_save):
             signals.post_save.connect(self.handlers.mute_block_receiver)

Unusable password generator for Django
#### The problem

The recently added `Password` generator for Django is helpful, but it's not clear how to use it to create an unusable password (similar to calling `set_unusable_password` on the generated user).

#### Proposed solution

Django's `set_unusable_password` is a call to `make_password` with `None` as the password argument:

https://github.com/django/django/blob/0b506bfe1ab9f1c38e439c77b3c3f81c8ac663ea/django/contrib/auth/base_user.py#L118-L120

Using `password = factory.django.Password(None)` will actually work (and will allow factory users to override the password if desired). However, currently the password argument to this factory is documented as a string and this option is not mentioned.

#### Extra notes

The default value of the `password` argument to `factory.django.Password` could also be set to `None`. This would make that factory generate unusable passwords by default, which may or may not be desired.

tests/test_django.py::PreventSignalsTestCase::test_signal_receiver_order_restored_after_mute_signals
tests/test_django.py::ModelTests::test_cross_database tests/test_django.py::ModelTests::test_unset_model tests/test_django.py::DjangoPkSequenceTestCase::test_pk_creation tests/test_django.py::DjangoPkSequenceTestCase::test_pk_first tests/test_django.py::DjangoPkSequenceTestCase::test_pk_force_value tests/test_django.py::DjangoPkSequenceTestCase::test_pk_many tests/test_django.py::DjangoGetOrCreateTests::test_missing_arg tests/test_django.py::DjangoGetOrCreateTests::test_multicall tests/test_django.py::DjangoGetOrCreateTests::test_simple_call tests/test_django.py::MultipleGetOrCreateFieldsTest::test_both_defined tests/test_django.py::MultipleGetOrCreateFieldsTest::test_one_defined tests/test_django.py::MultipleGetOrCreateFieldsTest::test_unique_field_not_in_get_or_create tests/test_django.py::DjangoPkForceTestCase::test_force_pk tests/test_django.py::DjangoPkForceTestCase::test_no_pk tests/test_django.py::DjangoPkForceTestCase::test_reuse_pk tests/test_django.py::DjangoModelLoadingTestCase::test_building tests/test_django.py::DjangoModelLoadingTestCase::test_inherited_loading tests/test_django.py::DjangoModelLoadingTestCase::test_inherited_loading_and_sequence tests/test_django.py::DjangoModelLoadingTestCase::test_loading tests/test_django.py::DjangoNonIntegerPkTestCase::test_creation tests/test_django.py::DjangoNonIntegerPkTestCase::test_first tests/test_django.py::DjangoNonIntegerPkTestCase::test_force_pk tests/test_django.py::DjangoNonIntegerPkTestCase::test_many tests/test_django.py::DjangoAbstractBaseSequenceTestCase::test_auto_sequence_grandson tests/test_django.py::DjangoAbstractBaseSequenceTestCase::test_auto_sequence_son tests/test_django.py::DjangoAbstractBaseSequenceTestCase::test_optional_abstract tests/test_django.py::DjangoRelatedFieldTestCase::test_create_pointed tests/test_django.py::DjangoRelatedFieldTestCase::test_create_pointed_related tests/test_django.py::DjangoRelatedFieldTestCase::test_create_pointed_related_extra tests/test_django.py::DjangoRelatedFieldTestCase::test_create_pointed_related_with_deep_context tests/test_django.py::DjangoRelatedFieldTestCase::test_create_pointed_related_with_trait tests/test_django.py::DjangoRelatedFieldTestCase::test_create_pointer tests/test_django.py::DjangoRelatedFieldTestCase::test_create_pointer_extra tests/test_django.py::DjangoRelatedFieldTestCase::test_create_pointer_with_deep_context tests/test_django.py::DjangoPasswordTestCase::test_build tests/test_django.py::DjangoPasswordTestCase::test_build_with_kwargs tests/test_django.py::DjangoPasswordTestCase::test_create tests/test_django.py::DjangoFileFieldTestCase::test_default_build tests/test_django.py::DjangoFileFieldTestCase::test_default_create tests/test_django.py::DjangoFileFieldTestCase::test_error_both_file_and_path tests/test_django.py::DjangoFileFieldTestCase::test_existing_file tests/test_django.py::DjangoFileFieldTestCase::test_no_file tests/test_django.py::DjangoFileFieldTestCase::test_override_filename_with_path tests/test_django.py::DjangoFileFieldTestCase::test_with_content tests/test_django.py::DjangoFileFieldTestCase::test_with_file tests/test_django.py::DjangoFileFieldTestCase::test_with_file_empty_path tests/test_django.py::DjangoFileFieldTestCase::test_with_path tests/test_django.py::DjangoFileFieldTestCase::test_with_path_empty_file tests/test_django.py::DjangoParamsTestCase::test_pointing_with_traits_using_same_name tests/test_django.py::DjangoParamsTestCase::test_undeclared_fields tests/test_django.py::DjangoFakerTestCase::test_random tests/test_django.py::DjangoImageFieldTestCase::test_complex_create tests/test_django.py::DjangoImageFieldTestCase::test_default_build tests/test_django.py::DjangoImageFieldTestCase::test_default_create tests/test_django.py::DjangoImageFieldTestCase::test_error_both_file_and_path tests/test_django.py::DjangoImageFieldTestCase::test_existing_file tests/test_django.py::DjangoImageFieldTestCase::test_gif tests/test_django.py::DjangoImageFieldTestCase::test_no_file tests/test_django.py::DjangoImageFieldTestCase::test_override_filename_with_path tests/test_django.py::DjangoImageFieldTestCase::test_rgba_image tests/test_django.py::DjangoImageFieldTestCase::test_with_content tests/test_django.py::DjangoImageFieldTestCase::test_with_file tests/test_django.py::DjangoImageFieldTestCase::test_with_file_empty_path tests/test_django.py::DjangoImageFieldTestCase::test_with_func tests/test_django.py::DjangoImageFieldTestCase::test_with_path tests/test_django.py::DjangoImageFieldTestCase::test_with_path_empty_file tests/test_django.py::PreventSignalsTestCase::test_class_decorator tests/test_django.py::PreventSignalsTestCase::test_class_decorator_build tests/test_django.py::PreventSignalsTestCase::test_class_decorator_related_model_with_post_hook tests/test_django.py::PreventSignalsTestCase::test_class_decorator_with_subfactory tests/test_django.py::PreventSignalsTestCase::test_classmethod_decorator tests/test_django.py::PreventSignalsTestCase::test_context_manager tests/test_django.py::PreventSignalsTestCase::test_function_decorator tests/test_django.py::PreventSignalsTestCase::test_receiver_created_during_model_instantiation_is_not_lost tests/test_django.py::PreventSignalsTestCase::test_signal_cache tests/test_django.py::PreventChainedSignalsTestCase::test_class_decorator_with_muted_related_factory tests/test_django.py::PreventChainedSignalsTestCase::test_class_decorator_with_muted_subfactory tests/test_django.py::DjangoCustomManagerTestCase::test_extra_args tests/test_django.py::DjangoCustomManagerTestCase::test_with_manager_on_abstract tests/test_django.py::DjangoModelFactoryDuplicateSaveDeprecationTest::test_build_no_warning tests/test_django.py::DjangoModelFactoryDuplicateSaveDeprecationTest::test_create_warning tests/test_django.py::IntegrityErrorForMissingOriginalParamsTest::test_raises_integrity_error