diff --git a/.gitignore b/.gitignore
index a661e32..54a2bac 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,7 +1,9 @@
+*.db
+*.egg-info
 *.log
 *.pot
 *.pyc
-*.db
-local_settings.py
-.pydevproject
+.idea
 .project
+.pydevproject
+local_settings.py
diff --git a/src/auditlog/diff.py b/src/auditlog/diff.py
index d22d2e0..109657b 100644
--- a/src/auditlog/diff.py
+++ b/src/auditlog/diff.py
@@ -1,5 +1,6 @@
 from __future__ import unicode_literals
 
+from django.conf import settings
 from django.core.exceptions import ObjectDoesNotExist
 from django.db.models import Model, NOT_PROVIDED, DateTimeField
 from django.utils import timezone
@@ -64,7 +65,7 @@ def get_field_value(obj, field):
         # to its naive form before we can accuratly compare them for changes.
         try:
             value = field.to_python(getattr(obj, field.name, None))
-            if value is not None:
+            if value is not None and settings.USE_TZ:
                 value = timezone.make_naive(value, timezone=timezone.utc)
         except ObjectDoesNotExist:
             value = field.default if field.default is not NOT_PROVIDED else None
diff --git a/src/auditlog/mixins.py b/src/auditlog/mixins.py
index 7e3c626..49b9d07 100644
--- a/src/auditlog/mixins.py
+++ b/src/auditlog/mixins.py
@@ -26,7 +26,7 @@ class LogEntryAdminMixin(object):
     def resource_url(self, obj):
         app_label, model = obj.content_type.app_label, obj.content_type.model
         viewname = 'admin:%s_%s_change' % (app_label, model)
-        link = urlresolvers.reverse(viewname, args=[obj.object_id])
+        link = urlresolvers.reverse(viewname, args=[obj.object_id or obj.object_pk])
         return u'<a href="%s">%s</a>' % (link, obj.object_repr)
     resource_url.allow_tags = True
     resource_url.short_description = 'Resource'