diff --git a/goodwe_controller/test_opt20.py b/goodwe_controller/test_opt20.py
index ec4d721..2f47cd8 100644
--- a/goodwe_controller/test_opt20.py
+++ b/goodwe_controller/test_opt20.py
@@ -19,7 +19,8 @@ its maintenance charge phase at 0 W, with the grid at 3100 W for 34 s.
 
 Out of scope, and unchanged: a normal (non-probing) trade placed on a battery
 in maintenance charge (OPT-11 P4 F4) and the action-log wording (UX-38).
-Mutations are listed in the pull request.
+Mutations: MUTATION.md says how to run them (purged copies); the 12 of
+OPT-20 are listed in the pull request.
 """
 
 import dataclasses