diff --git a/pyrfc3339/tests/test_all.py b/pyrfc3339/tests/test_all.py
index b31ec38..24636b2 100644
--- a/pyrfc3339/tests/test_all.py
+++ b/pyrfc3339/tests/test_all.py
@@ -106,6 +106,10 @@ def test_generate_local_parse_utc(self):
         dt2 = parse(generate(dt1, utc=False, microseconds=True))
         self.assertEqual(dt1, dt2)
 
+    def test_three_digit_year(self):
+        dt = datetime(999,1,1,0,0,0, tzinfo=timezone.utc)
+        self.assertEqual(generate(dt), "0999-01-01T00:00:00Z")
+
 
 class TestExhaustiveRoundtrip(unittest.TestCase):
     """