diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8b1baac6a..befc05758 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,11 +1,14 @@
 # Changelog
 
-# Version 3.21.0 (in progress)
+# Version 3.21.0
 ## Added
   * Projects can be created with a `media_type`
   * Added `media_type` attribute to `Project`
   * New `MediaType` enumeration
 
+## Fix
+  * Added back the mimetype to datarow bulk uploads for orgs that require delegated access
+
 # Version 3.20.1 (2022-05-02)
 ## Updated
 * Ontology Classification `scope` field is only set for top level classifications
diff --git a/labelbox/__init__.py b/labelbox/__init__.py
index 5857460bc..7d4e16315 100644
--- a/labelbox/__init__.py
+++ b/labelbox/__init__.py
@@ -1,11 +1,11 @@
 name = "labelbox"
-__version__ = "3.20.1"
+__version__ = "3.21.0"
 
 import sys
 import warnings
 
 if sys.version_info < (3, 7):
-    warnings.warn("""Python 3.6 will no longer be actively supported 
+    warnings.warn("""Python 3.6 will no longer be actively supported
     starting 06/01/2022. Please upgrade to Python 3.7 or higher.""")
 
 from labelbox.client import Client
diff --git a/labelbox/schema/dataset.py b/labelbox/schema/dataset.py
index 0a5d45251..6fe8ec86e 100644
--- a/labelbox/schema/dataset.py
+++ b/labelbox/schema/dataset.py
@@ -314,7 +314,9 @@ def convert_item(item):
             items = [future.result() for future in as_completed(futures)]
         # Prepare and upload the desciptor file
         data = json.dumps(items)
-        return self.client.upload_data(data)
+        return self.client.upload_data(data,
+                                       content_type="application/json",
+                                       filename="json_import.json")
 
     def data_rows_for_external_id(self,
                                   external_id,
diff --git a/tests/integration/test_dataset.py b/tests/integration/test_dataset.py
index e464a30a8..5fd3a6271 100644
--- a/tests/integration/test_dataset.py
+++ b/tests/integration/test_dataset.py
@@ -109,3 +109,19 @@ def test_data_row_export(dataset, image_url):
     result = list(dataset.export_data_rows())
     assert len(result) == n_data_rows
     assert set(result) == ids
+
+
+def test_create_descriptor_file(dataset):
+    import unittest.mock as mock
+    with mock.patch.object(dataset.client,
+                           'upload_data',
+                           wraps=dataset.client.upload_data) as upload_data_spy:
+        dataset._create_descriptor_file(items=[{'row_data': 'some text...'}])
+        upload_data_spy.assert_called()
+        call_args, call_kwargs = upload_data_spy.call_args_list[0][
+            0], upload_data_spy.call_args_list[0][1]
+        assert call_args == ('[{"data": "some text..."}]',)
+        assert call_kwargs == {
+            'content_type': 'application/json',
+            'filename': 'json_import.json'
+        }