diff --git a/swh/storage/cassandra/storage.py b/swh/storage/cassandra/storage.py
--- a/swh/storage/cassandra/storage.py
+++ b/swh/storage/cassandra/storage.py
@@ -303,7 +303,7 @@
         self, contents: List[Sha1Git]
     ) -> Iterable[Sha1Git]:
         return self.content_missing(
-            [{"sha1_git": c for c in contents}], key_hash="sha1_git"
+            [{"sha1_git": c} for c in contents], key_hash="sha1_git"
         )
 
     def content_get_random(self) -> Sha1Git:
diff --git a/swh/storage/tests/storage_tests.py b/swh/storage/tests/storage_tests.py
--- a/swh/storage/tests/storage_tests.py
+++ b/swh/storage/tests/storage_tests.py
@@ -499,13 +499,22 @@
     def test_content_missing_per_sha1_git(self, swh_storage, sample_data):
         cont, cont2 = sample_data.contents[:2]
         missing_cont = sample_data.skipped_content
+        missing_cont2 = sample_data.skipped_content2
 
         swh_storage.content_add([cont, cont2])
 
-        contents = [cont.sha1_git, cont2.sha1_git, missing_cont.sha1_git]
+        contents = [
+            cont.sha1_git,
+            cont2.sha1_git,
+            missing_cont.sha1_git,
+            missing_cont2.sha1_git,
+        ]
 
         missing_contents = swh_storage.content_missing_per_sha1_git(contents)
-        assert list(missing_contents) == [missing_cont.sha1_git]
+        assert list(missing_contents) == [missing_cont.sha1_git, missing_cont2.sha1_git]
+
+        missing_contents = swh_storage.content_missing_per_sha1_git([])
+        assert list(missing_contents) == []
 
     def test_content_get_partition(self, swh_storage, swh_contents):
         """content_get_partition paginates results if limit exceeded"""