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
@@ -77,6 +77,11 @@
 objstorage = None
 
 
+@app.errorhandler(ObjNotFoundError)
+def not_found_error_handler(exception):
+    return error_handler(exception, encode_data, status_code=404)
+
+
 @app.errorhandler(Error)
 def argument_error_handler(exception):
     return error_handler(exception, encode_data, status_code=400)
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
@@ -1,4 +1,4 @@
-# Copyright (C) 2015-2020  The Software Heritage developers
+# Copyright (C) 2015-2022  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -115,7 +115,7 @@
 
     def test_check_missing(self):
         content, obj_id = self.hash_content(b"check_missing")
-        with self.assertRaises(exc.Error):
+        with self.assertRaises(exc.ObjNotFoundError):
             self.storage.check(obj_id)
 
     def test_check_present(self):
diff --git a/swh/objstorage/tests/test_objstorage_api.py b/swh/objstorage/tests/test_objstorage_api.py
--- a/swh/objstorage/tests/test_objstorage_api.py
+++ b/swh/objstorage/tests/test_objstorage_api.py
@@ -1,13 +1,15 @@
-# Copyright (C) 2015-2020  The Software Heritage developers
+# Copyright (C) 2015-2022  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+from hashlib import sha1
 import shutil
 import tempfile
 import unittest
 
 import pytest
+import requests
 
 from swh.core.api.tests.server_testing import ServerTestFixture
 from swh.objstorage.api.server import app
@@ -38,6 +40,13 @@
         super().tearDown()
         shutil.rmtree(self.tmpdir)
 
+    def test_404_status_code_on_missing_object(self):
+        response = requests.post(
+            self.url() + "content/get",
+            json={"obj_id": sha1(b"missing").hexdigest()},
+        )
+        assert response.status_code == 404
+
     @pytest.mark.skip("makes no sense to test this for the remote api")
     def test_delete_not_allowed(self):
         pass