diff --git a/dcicutils/contribution_utils.py b/dcicutils/contribution_utils.py
index 1b0229610..d5fba1162 100644
--- a/dcicutils/contribution_utils.py
+++ b/dcicutils/contribution_utils.py
@@ -213,23 +213,30 @@ def contributor_values_as_objects(cls, contributor_index: Optional[Dict]) -> Opt
         if contributor_index is None:
             return None
         else:
-            items = contributor_index.items()
-            key: str
-            result = {
+            return {
                 key: Contributor.from_dict(value)
-                for key, value in items
+                for key, value in contributor_index.items()
             }
-            return result
 
     def checkpoint_state(self):
         return self.as_dict()
 
     def as_dict(self):
-        data = {
-            "forked_at": self.forked_at.isoformat() if self.forked_at else None,
-            "pre_fork_contributors_by_name": self.contributor_values_as_dicts(self.pre_fork_contributors_by_name),
-            "contributors_by_name": self.contributor_values_as_dicts(self.contributors_by_name),
-        }
+
+        data = {}
+
+        forked_at = self.forked_at.isoformat() if self.forked_at else None
+        if forked_at is not None:
+            data["forked_at"] = forked_at
+
+        pre_fork_contributors_by_name = self.contributor_values_as_dicts(self.pre_fork_contributors_by_name)
+        if pre_fork_contributors_by_name is not None:
+            data["pre_fork_contributors_by_name"] = pre_fork_contributors_by_name
+
+        contributors_by_name = self.contributor_values_as_dicts(self.contributors_by_name)
+        if contributors_by_name is not None:
+            data["contributors_by_name"] = contributors_by_name
+
         return data
 
     def save_contributor_data(self, filename: Optional[str] = None) -> str:
diff --git a/test/test_contribution_utils.py b/test/test_contribution_utils.py
index 1095480e6..7f8ca2870 100644
--- a/test/test_contribution_utils.py
+++ b/test/test_contribution_utils.py
@@ -578,24 +578,28 @@ def test_save_contributor_data():
 
         contributions = BasicContributions()
         cache_file = contributions.save_contributor_data()
+        assert json.loads(file_contents(cache_file)) == {}
 
-        assert file_contents(cache_file) == (
-            '{\n'
-            '  "forked_at": null,\n'
-            '  "pre_fork_contributors_by_name": null,\n'
-            '  "contributors_by_name": null\n'
-            '}\n'
-        )
+        contributions = BasicContributions()
+        contributions.forked_at = datetime.datetime(2020, 1, 1, 12, 34, 56)
+        contributions.pre_fork_contributors_by_name = {}
+        contributions.contributors_by_name = contributions.contributor_values_as_objects({
+            "Joe": {"names": ["Joe"], "emails": ["joe@foo"]}
+        })
+        cache_file = contributions.save_contributor_data()
+        assert json.loads(file_contents(cache_file)) == {
+            "forked_at": "2020-01-01T12:34:56",
+            "pre_fork_contributors_by_name": {},
+            "contributors_by_name": {"Joe": {"names": ["Joe"], "emails": ["joe@foo"]}}
+        }
 
         cache_file_2 = contributions.save_contributor_data('some.file')
         assert cache_file_2 == 'some.file'
-        assert file_contents(cache_file_2) == (
-            '{\n'
-            '  "forked_at": null,\n'
-            '  "pre_fork_contributors_by_name": null,\n'
-            '  "contributors_by_name": null\n'
-            '}\n'
-        )
+        assert json.loads(file_contents(cache_file_2)) == {
+            "forked_at": "2020-01-01T12:34:56",
+            "pre_fork_contributors_by_name": {},
+            "contributors_by_name": {"Joe": {"names": ["Joe"], "emails": ["joe@foo"]}}
+        }
 
 
 def test_repo_contributor_names():