diff --git a/pageserver/src/tenant/timeline/detach_ancestor.rs b/pageserver/src/tenant/timeline/detach_ancestor.rs
index b3c078312e..4fd6e054b2 100644
--- a/pageserver/src/tenant/timeline/detach_ancestor.rs
+++ b/pageserver/src/tenant/timeline/detach_ancestor.rs
@@ -302,6 +302,8 @@ impl SharedState {
             .get(&attempt.timeline_id)
             .cloned()
         else {
+            // no need to cancel the attempt, because timeline deletion and/or tenant restart has
+            // already marked it unblocked.
             return Err(Error::DetachedNotFoundAfterRestart);
         };