diff --git a/swh/storage/in_memory.py b/swh/storage/in_memory.py
--- a/swh/storage/in_memory.py
+++ b/swh/storage/in_memory.py
@@ -289,8 +289,10 @@
             hash = content.get(algo)
             if hash and hash in self._content_indexes[algo]:
                 found.append(self._content_indexes[algo][hash])
+
         if not found:
-            return
+            return []
+
         keys = list(set.intersection(*found))
         return copy.deepcopy([self._contents[key] for key in keys])
 
diff --git a/swh/storage/storage.py b/swh/storage/storage.py
--- a/swh/storage/storage.py
+++ b/swh/storage/storage.py
@@ -516,12 +516,8 @@
                                    sha256=content.get('sha256'),
                                    blake2s256=content.get('blake2s256'),
                                    cur=cur)
-        if contents:
-            contents_list = []
-            for cont in contents:
-                contents_list.append(dict(zip(db.content_find_cols, cont)))
-            return contents_list
-        return None
+        return [dict(zip(db.content_find_cols, content))
+                for content in contents]
 
     @db_transaction()
     def directory_add(self, directories, db, cur):
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
@@ -2494,19 +2494,19 @@
         actually_present = self.storage.content_find(
             {'sha1': missing_cont['sha1']})
 
-        self.assertIsNone(actually_present)
+        self.assertEqual(actually_present, [])
 
         # 2. with something that does not exist
         actually_present = self.storage.content_find(
             {'sha1_git': missing_cont['sha1_git']})
 
-        self.assertIsNone(actually_present)
+        self.assertEqual(actually_present, [])
 
         # 3. with something that does not exist
         actually_present = self.storage.content_find(
             {'sha256': missing_cont['sha256']})
 
-        self.assertIsNone(actually_present)
+        self.assertEqual(actually_present, [])
 
     def test_content_find_with_duplicate_input(self):
         cont1 = self.cont