diff --git a/rest_framework_gis/serializers.py b/rest_framework_gis/serializers.py
index e42852e8..44765d03 100644
--- a/rest_framework_gis/serializers.py
+++ b/rest_framework_gis/serializers.py
@@ -151,7 +151,10 @@ def get_properties(self, instance, fields):
             if field.write_only:
                 continue
             value = field.get_attribute(instance)
-            properties[field.field_name] = field.to_representation(value)
+            value_repr = None
+            if value is not None:
+                value_repr = field.to_representation(value)
+            properties[field.field_name] = value_repr
 
         return properties
 
diff --git a/tests/django_restframework_gis_tests/models.py b/tests/django_restframework_gis_tests/models.py
index f9c5fdd6..278bfe1a 100644
--- a/tests/django_restframework_gis_tests/models.py
+++ b/tests/django_restframework_gis_tests/models.py
@@ -12,6 +12,7 @@
 class BaseModel(models.Model):
     name = models.CharField(max_length=32)
     slug = models.SlugField(max_length=128, unique=True, blank=True)
+    timestamp = models.DateTimeField(null=True, blank=True)
     geometry = models.GeometryField()
     objects = models.GeoManager()
 
diff --git a/tests/django_restframework_gis_tests/serializers.py b/tests/django_restframework_gis_tests/serializers.py
index 6b08bfb5..c4e767e9 100644
--- a/tests/django_restframework_gis_tests/serializers.py
+++ b/tests/django_restframework_gis_tests/serializers.py
@@ -54,7 +54,7 @@ class Meta:
         model = Location
         geo_field = 'geometry'
         id_field = 'slug'
-        fields = ('name', 'slug')
+        fields = ('name', 'slug', 'timestamp')
 
 
 class LocationGeoFeatureFalseIdSerializer(LocationGeoFeatureSerializer):
@@ -98,7 +98,7 @@ class Meta:
         model = BoxedLocation
         geo_field = 'geometry'
         bbox_geo_field = 'bbox_geometry'
-        fields = ['name', 'details', 'id']
+        fields = ['name', 'details', 'id', 'timestamp']
 
 
 class LocationGeoFeatureBboxSerializer(gis_serializers.GeoFeatureModelSerializer):
diff --git a/tests/django_restframework_gis_tests/tests.py b/tests/django_restframework_gis_tests/tests.py
index d5ceb013..a3d78bbc 100644
--- a/tests/django_restframework_gis_tests/tests.py
+++ b/tests/django_restframework_gis_tests/tests.py
@@ -228,6 +228,7 @@ def test_geojson_format(self):
                 'details': "http://testserver/geojson/%s/" % location.id,
                 'name': 'geojson test',
                 'fancy_name': 'Kool geojson test',
+                'timestamp': None,
                 'slug': 'geojson-test',
             },
             'geometry': {