diff --git a/src/ampform_dpd/io/serialization/__init__.py b/src/ampform_dpd/io/serialization/__init__.py
index 297f29b..c9530d7 100644
--- a/src/ampform_dpd/io/serialization/__init__.py
+++ b/src/ampform_dpd/io/serialization/__init__.py
@@ -1,5 +1,9 @@
 """Amplitude model serialization
 
-See :doc:`/usage/serialization` for more information and
-`https://rub-ep1.github.io/amplitude-serialization/`_ for more information.
+See :doc:`/serialization` for more information and
+https://rub-ep1.github.io/amplitude-serialization for more information.
+
+.. warning::
+    This module is in preview, see https://github.com/ComPWA/ampform-dpd/issues/133 for
+    updates.
 """