diff --git a/maya/core.py b/maya/core.py
index de55115..dc26c1d 100644
--- a/maya/core.py
+++ b/maya/core.py
@@ -277,7 +277,7 @@ def rfc2822(self):
 
     def rfc3339(self):
         """Returns an RFC 3339 representation of the MayaDT."""
-        return self.datetime().strftime("%Y-%m-%dT%H:%M:%S.%f")[:-4] + "Z"
+        return self.datetime().strftime("%Y-%m-%dT%H:%M:%S.%f")[:-5] + "Z"
 
     # Properties
     # ----------
diff --git a/tests/test_maya.py b/tests/test_maya.py
index 39377d7..8082c02 100644
--- a/tests/test_maya.py
+++ b/tests/test_maya.py
@@ -245,6 +245,11 @@ def test_rfc3339():
     mdt2 = maya.MayaDT.from_rfc3339(out)
     assert mdt.epoch == mdt2.epoch
 
+    rfc3339 = maya.MayaDT.rfc3339(maya.when('2016-01-01T12:03:03Z'))
+    # it's important that the string has got a "max 1-digit millis" fragment
+    # as per https://tools.ietf.org/html/rfc3339#section-5.6
+    assert rfc3339 == '2016-01-01T12:03:03.0Z'
+
 
 @pytest.mark.usefixtures("frozen_now")
 def test_comparison_operations():