diff --git a/swh/storage/api/client.py b/swh/storage/api/client.py
--- a/swh/storage/api/client.py
+++ b/swh/storage/api/client.py
@@ -3,7 +3,10 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+from typing import Any, Dict, Iterable, Union
+
 from swh.core.api import RPCClient, RemoteException
+from swh.model.model import Content
 
 from .. import HashCollision
 from ..exc import StorageAPIError, StorageArgumentException
@@ -35,6 +38,11 @@
             else:
                 raise
 
+    def content_add(self, content: Iterable[Union[Content, Dict[str, Any]]]):
+        content = [c.with_data() if isinstance(c, Content) else c
+                   for c in content]
+        return self.post('content/add', {'content': content})
+
     def reset(self):
         return self.post('reset', {})
 
diff --git a/swh/storage/objstorage.py b/swh/storage/objstorage.py
--- a/swh/storage/objstorage.py
+++ b/swh/storage/objstorage.py
@@ -5,7 +5,7 @@
 
 from typing import Dict, Generator, Iterable
 
-from swh.model.model import Content
+from swh.model.model import Content, MissingData
 from swh.objstorage import get_objstorage
 from swh.objstorage.exc import ObjNotFoundError
 
@@ -52,9 +52,10 @@
             objstorage.
 
         """
-        contents = list(contents)
-        if any(cont.data is None for cont in contents):
-            raise StorageArgumentException('Missing data')
+        try:
+            contents = [c.with_data() for c in contents]
+        except MissingData:
+            raise StorageArgumentException('Missing data') from None
         summary = self.objstorage.add_batch({
             cont.sha1: cont.data
             for cont in contents
diff --git a/swh/storage/tests/test_api_client_dicts.py b/swh/storage/tests/test_api_client_dicts.py
--- a/swh/storage/tests/test_api_client_dicts.py
+++ b/swh/storage/tests/test_api_client_dicts.py
@@ -67,3 +67,7 @@
         swh_storage.journal_writer.journal = None
         with patch.object(server.storage.journal_writer, 'journal', None):
             super().test_content_update(swh_storage)
+
+    @pytest.mark.skip('non-applicable test')
+    def test_content_add_from_lazy_content(self):
+        pass
diff --git a/swh/storage/tests/test_storage.py b/swh/storage/tests/test_storage.py
--- a/swh/storage/tests/test_storage.py
+++ b/swh/storage/tests/test_storage.py
@@ -26,7 +26,7 @@
 
 from swh.model import from_disk, identifiers
 from swh.model.hashutil import hash_to_bytes
-from swh.model.model import Release, Revision
+from swh.model.model import Content, Release, Revision
 from swh.model.hypothesis_strategies import objects
 from swh.storage import HashCollision, get_storage
 from swh.storage.converters import origin_url_to_sha1 as sha1
@@ -175,6 +175,53 @@
         swh_storage.refresh_stat_counters()
         assert swh_storage.stat_counters()['content'] == 1
 
+    def test_content_add_from_lazy_content(self, swh_storage):
+        called = False
+        cont = data.cont
+
+        class LazyContent(Content):
+            def with_data(self):
+                nonlocal called
+                called = True
+                return Content.from_dict({
+                    **self.to_dict(),
+                    'data': cont['data']
+                })
+
+        lazy_content = LazyContent.from_dict({
+            **cont,
+            'data': b'nope',
+        })
+
+        insertion_start_time = datetime.datetime.now(tz=datetime.timezone.utc)
+
+        # bypass the validation proxy for now, to directly put a dict
+        actual_result = swh_storage.storage.content_add([lazy_content])
+
+        insertion_end_time = datetime.datetime.now(tz=datetime.timezone.utc)
+
+        assert actual_result == {
+            'content:add': 1,
+            'content:add:bytes': cont['length'],
+        }
+
+        assert called
+
+        assert list(swh_storage.content_get([cont['sha1']])) == \
+            [{'sha1': cont['sha1'], 'data': cont['data']}]
+
+        expected_cont = data.cont
+        del expected_cont['data']
+        journal_objects = list(swh_storage.journal_writer.journal.objects)
+        for (obj_type, obj) in journal_objects:
+            assert insertion_start_time <= obj['ctime']
+            assert obj['ctime'] <= insertion_end_time
+            del obj['ctime']
+        assert journal_objects == [('content', expected_cont)]
+
+        swh_storage.refresh_stat_counters()
+        assert swh_storage.stat_counters()['content'] == 1
+
     def test_content_add_validation(self, swh_storage):
         cont = data.cont