diff --git a/src/dirtyfields/dirtyfields.py b/src/dirtyfields/dirtyfields.py
index 49023fa..54ea30f 100644
--- a/src/dirtyfields/dirtyfields.py
+++ b/src/dirtyfields/dirtyfields.py
@@ -1,9 +1,9 @@
 from copy import deepcopy
-
 from django.core.exceptions import ValidationError
 from django.db.models.expressions import BaseExpression
 from django.db.models.expressions import Combinable
 from django.db.models.signals import post_save, m2m_changed
+from django.utils import timezone
 
 from .compare import raw_compare, compare_states, normalise_value
 
@@ -83,6 +83,9 @@ def _as_dict(self, check_relationship, include_primary_key=True):
             if isinstance(field_value, (BaseExpression, Combinable)):
                 continue
 
+            if isinstance(field_value, timezone.datetime) and field.auto_now:
+                field_value = timezone.now()
+
             try:
                 # Store the converted value for fields with conversion
                 field_value = field.to_python(field_value)
diff --git a/tests/models.py b/tests/models.py
index b2dd9e9..f879593 100644
--- a/tests/models.py
+++ b/tests/models.py
@@ -69,6 +69,10 @@ class DatetimeModelTest(DirtyFieldsMixin, models.Model):
     datetime_field = models.DateTimeField(default=django_timezone.now)
 
 
+class UpdatedDatetimeModelTest(DirtyFieldsMixin, models.Model):
+    updated_datetime_field = models.DateTimeField(auto_now=True)
+
+
 class CurrentDatetimeModelTest(DirtyFieldsMixin, models.Model):
     compare_function = (
         timezone_support_compare,
diff --git a/tests/test_timezone_aware_fields.py b/tests/test_timezone_aware_fields.py
index 381d68a..1435c21 100644
--- a/tests/test_timezone_aware_fields.py
+++ b/tests/test_timezone_aware_fields.py
@@ -4,7 +4,7 @@
 from django.test.utils import override_settings
 from django.utils import timezone as django_timezone
 
-from .models import DatetimeModelTest, CurrentDatetimeModelTest
+from .models import DatetimeModelTest, CurrentDatetimeModelTest, UpdatedDatetimeModelTest
 
 
 @override_settings(USE_TZ=True)
@@ -107,3 +107,10 @@ def test_datetime_fields_with_current_timezone_conversion_without_timezone_suppo
         ),
     ):
         assert tm.get_dirty_fields() == {}
+
+
+@pytest.mark.django_db
+def test_updated_datetime_fields():
+    tm = UpdatedDatetimeModelTest.objects.create()
+    tm.id = 2
+    assert list(tm.get_dirty_fields().keys()) == ['id', 'updated_datetime_field']