diff --git a/goodwe_controller/test_ux54_dst.py b/goodwe_controller/test_ux54_dst.py
index 6dbe47c..850873b 100644
--- a/goodwe_controller/test_ux54_dst.py
+++ b/goodwe_controller/test_ux54_dst.py
@@ -18,6 +18,8 @@ that the add-on's own `except Exception` cannot swallow (`Hang` is a
    hours with the local hour labels of that day, every level inside floor
    and ceiling, every block inside its day.
 3. `SolarToday` keeps the two 02:00 hours of the autumn change apart.
+
+Mutating what this file grades? Read MUTATION.md first (stale bytecode).
 """
 
 import logging