diff --git a/swh/storage/converters.py b/swh/storage/converters.py
--- a/swh/storage/converters.py
+++ b/swh/storage/converters.py
@@ -52,6 +52,8 @@
         dict: a dictionary with four keys: id, fullname, name and email, or
         None if the id is None
     """
+    if (fullname, name, email) == (None, None, None):
+        return None
     return {
         "fullname": fullname,
         "name": name,
diff --git a/swh/storage/tests/test_converters.py b/swh/storage/tests/test_converters.py
--- a/swh/storage/tests/test_converters.py
+++ b/swh/storage/tests/test_converters.py
@@ -55,6 +55,14 @@
     }
 
 
+def test_db_to_author_none():
+    # when
+    actual_author = converters.db_to_author(None, None, None)
+
+    # then
+    assert actual_author is None
+
+
 def test_db_to_revision():
     # when
     actual_revision = converters.db_to_revision(