diff --git a/03-DESIGN/01-to-be/47-milestones/G-20-lead-answers.md b/03-DESIGN/01-to-be/47-milestones/G-20-lead-answers.md
index 5639d495..6af3b904 100644
--- a/03-DESIGN/01-to-be/47-milestones/G-20-lead-answers.md
+++ b/03-DESIGN/01-to-be/47-milestones/G-20-lead-answers.md
@@ -577,3 +577,7 @@ names the principle that settles it, and is cited as "design 47 G A-n".
 - **A-154** (design 46 approval mark §4, §16, §19; principles 7 and 8) The approval mark's three findings take scope
   `machine` and the id `<node>.<module>`, `<node>.<ask id>` or `<node>.approvals`, escaped as a key's name, with the
   subject of the tool runner on that machine, as the runner's first-view findings already do.
+- **A-155** (§561, §563, §302, A-77; principles 1, 2 and 3) restic's put-off wait for a restore is a bound key in a
+  state of its own on the bus, bounded by the setting `put-off-bound`: the key is the put-off record `backed-up` reads,
+  its expiry raises `backup-waits` and ends the wait, so the night never holds its lock without a bound and no file
+  or timer keeps it. BKP7 is not built: §555 gives `restore` its class's default with no own-item limit.