diff --git a/tests/test_api.py b/tests/test_api.py
index 8f6f6c9e37..125bf64386 100755
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -639,6 +639,13 @@ def test_targetfile_from_file(self) -> None:
         with self.assertRaises(ValueError):
             TargetFile.from_file(file_path, file_path, ["123"])
 
+    def test_targetfile_custom(self) -> None:
+        # Test creating TargetFile and accessing custom.
+        targetfile = TargetFile(
+            100, {"sha256": "abc"}, "file.txt", {"custom": "foo"}
+        )
+        self.assertEqual(targetfile.custom, "foo")
+
     def test_targetfile_from_data(self) -> None:
         data = b"Inline test content"
         target_file_path = os.path.join(
diff --git a/tests/test_metadata_serialization.py b/tests/test_metadata_serialization.py
index 3714eec00c..497eb1768d 100644
--- a/tests/test_metadata_serialization.py
+++ b/tests/test_metadata_serialization.py
@@ -214,6 +214,7 @@ def test_invalid_root_serialization(self, test_case_data: str) -> None:
 
     invalid_metafiles: utils.DataSet = {
         "wrong length type": '{"version": 1, "length": "a", "hashes": {"sha256" : "abc"}}',
+        "version 0": '{"version": 0, "length": 1, "hashes": {"sha256" : "abc"}}',
         "length 0": '{"version": 1, "length": 0, "hashes": {"sha256" : "abc"}}',
         "length below 0": '{"version": 1, "length": -1, "hashes": {"sha256" : "abc"}}',
         "empty hashes dict": '{"version": 1, "length": 1, "hashes": {}}',