diff --git a/swh/objstorage/api/client.py b/swh/objstorage/api/client.py
--- a/swh/objstorage/api/client.py
+++ b/swh/objstorage/api/client.py
@@ -8,7 +8,7 @@
 from swh.model import hashutil
 
 from ..objstorage import ObjStorage, DEFAULT_CHUNK_SIZE
-from ..exc import ObjStorageAPIError
+from ..exc import ObjNotFoundError, ObjStorageAPIError
 
 
 class RemoteObjStorage(ObjStorage, SWHRemoteAPI):
@@ -37,7 +37,11 @@
                                          'check_presence': check_presence})
 
     def get(self, obj_id):
-        return self.post('content/get', {'obj_id': obj_id})
+        ret = self.post('content/get', {'obj_id': obj_id})
+        if ret is None:
+            raise ObjNotFoundError(obj_id)
+        else:
+            return ret
 
     def get_batch(self, obj_ids):
         return self.post('content/get/batch', {'obj_ids': obj_ids})
diff --git a/swh/objstorage/api/server.py b/swh/objstorage/api/server.py
--- a/swh/objstorage/api/server.py
+++ b/swh/objstorage/api/server.py
@@ -12,6 +12,7 @@
                                 encode_data_server as encode_data)
 from swh.model import hashutil
 from swh.objstorage import get_objstorage
+from swh.objstorage.exc import ObjNotFoundError
 
 
 DEFAULT_CONFIG_PATH = 'objstorage/server'
@@ -51,7 +52,16 @@
 @asyncio.coroutine
 def get_bytes(request):
     req = yield from decode_request(request)
-    return encode_data(request.app['objstorage'].get(**req))
+    try:
+        ret = request.app['objstorage'].get(**req)
+    except ObjNotFoundError:
+        ret = {
+            'error': 'object_not_found',
+            'request': req,
+        }
+        return encode_data(ret, status=404)
+    else:
+        return encode_data(ret)
 
 
 @asyncio.coroutine
diff --git a/swh/objstorage/cloud/objstorage_azure.py b/swh/objstorage/cloud/objstorage_azure.py
--- a/swh/objstorage/cloud/objstorage_azure.py
+++ b/swh/objstorage/cloud/objstorage_azure.py
@@ -101,7 +101,7 @@
                 container_name=self.container_name,
                 blob_name=hex_obj_id)
         except AzureMissingResourceHttpError:
-            raise ObjNotFoundError('Content %s not found!' % hex_obj_id)
+            raise ObjNotFoundError(obj_id)
 
         return gzip.decompress(blob.content)
 
diff --git a/swh/objstorage/cloud/objstorage_cloud.py b/swh/objstorage/cloud/objstorage_cloud.py
--- a/swh/objstorage/cloud/objstorage_cloud.py
+++ b/swh/objstorage/cloud/objstorage_cloud.py
@@ -139,7 +139,7 @@
         try:
             return self.driver.get_object(self.container_name, hex_obj_id)
         except ObjectDoesNotExistError as e:
-            raise ObjNotFoundError(e.object_name)
+            raise ObjNotFoundError(obj_id)
 
     def _put_object(self, content, obj_id):
         """Create an object in the cloud storage.
diff --git a/swh/objstorage/tests/objstorage_testing.py b/swh/objstorage/tests/objstorage_testing.py
--- a/swh/objstorage/tests/objstorage_testing.py
+++ b/swh/objstorage/tests/objstorage_testing.py
@@ -90,9 +90,11 @@
     @istest
     def get_missing(self):
         content, obj_id = self.hash_content(b'get_missing')
-        with self.assertRaises(exc.Error):
+        with self.assertRaises(exc.ObjNotFoundError) as e:
             self.storage.get(obj_id)
 
+        self.assertIn(obj_id, e.exception.args)
+
     @istest
     def check_missing(self):
         content, obj_id = self.hash_content(b'check_missing')