diff --git a/tests/test_ydocs.py b/tests/test_ydocs.py
index 55e8d45..6f68385 100644
--- a/tests/test_ydocs.py
+++ b/tests/test_ydocs.py
@@ -1,3 +1,6 @@
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+
 from jupyter_ydoc import YBlob