diff --git a/swh/vault/cookers/revision_gitfast.py b/swh/vault/cookers/revision_gitfast.py
--- a/swh/vault/cookers/revision_gitfast.py
+++ b/swh/vault/cookers/revision_gitfast.py
@@ -108,6 +108,21 @@
         )
         self.obj_done.add(obj_id)
 
+    def _author_tuple_format(self, author, date):
+        # We never want to have None values here so we replace null entries
+        # by ''.
+        if author is not None:
+            author_tuple = (author.get('name') or b'',
+                            author.get('email') or b'')
+        else:
+            author_tuple = (b'', b'')
+        if date is not None:
+            date_tuple = (date.get('timestamp', {}).get('seconds') or 0,
+                          (date.get('offset') or 0) * 60)
+        else:
+            date_tuple = (0, 0)
+        return author_tuple + date_tuple
+
     def _compute_commit_command(self, rev):
         """Compute a commit command from a specific revision.
         """
@@ -128,20 +143,15 @@
         files = yield from self._compute_file_commands(rev, parent)
 
         # Construct and yield the commit command
-        author = (rev['author']['name'],
-                  rev['author']['email'],
-                  rev['date']['timestamp']['seconds'],
-                  rev['date']['offset'] * 60)
-        committer = (rev['committer']['name'],
-                     rev['committer']['email'],
-                     rev['committer_date']['timestamp']['seconds'],
-                     rev['committer_date']['offset'] * 60)
+        author = self._author_tuple_format(rev['author'], rev['date'])
+        committer = self._author_tuple_format(rev['committer'],
+                                              rev['committer_date'])
         yield fastimport.commands.CommitCommand(
             ref=b'refs/heads/master',
             mark=self.mark(rev['id']),
             author=author,
             committer=committer,
-            message=rev['message'],
+            message=rev['message'] or b'',
             from_=from_,
             merges=merges,
             file_iter=files,
diff --git a/swh/vault/tests/test_cookers.py b/swh/vault/tests/test_cookers.py
--- a/swh/vault/tests/test_cookers.py
+++ b/swh/vault/tests/test_cookers.py
@@ -385,3 +385,37 @@
             self.assertEqual((p / 'file').stat().st_mode, 0o100644)
             self.assertEqual((p / 'executable').stat().st_mode, 0o100755)
             self.assertEqual((p / 'wat').stat().st_mode, 0o100644)
+
+    def test_revision_null_fields(self):
+        # Our schema doesn't enforce a lot of non-null revision fields. We need
+        # to check these cases don't break the cooker.
+        repo = TestRepo()
+        with repo as rp:
+            (rp / 'file').write_text(TEST_CONTENT)
+            c = repo.commit('initial commit')
+            self.load(str(rp))
+            repo.repo.refs[b'HEAD'].decode()
+            dir_id_hex = repo.repo[c].tree.decode()
+            dir_id = hashutil.hash_to_bytes(dir_id_hex)
+
+        test_id = b'56789012345678901234'
+        test_revision = {
+            'id': test_id,
+            'message': None,
+            'author': {'name': None, 'email': None, 'fullname': ''},
+            'date': {'timestamp': 0, 'offset': 0, 'negative_utc': None},
+            'committer': {'name': None, 'email': None, 'fullname': ''},
+            'committer_date': {'timestamp': 0, 'offset': 0,
+                               'negative_utc': None},
+            'parents': [],
+            'type': 'git',
+            'directory': dir_id,
+            'metadata': {},
+            'synthetic': True
+        }
+
+        self.storage.revision_add([test_revision])
+
+        with self.cook_extract_revision_gitfast(test_id) as (ert, p):
+            ert.checkout(b'HEAD')
+            self.assertEqual((p / 'file').stat().st_mode, 0o100644)