While investigating https://pharo.fogbugz.com/f/cases/12640/PhLTitledTreeModel-refresh-called-to... I came across the following behaviour... 1. In Workspace do... "Announcer new inspect." 2. In that Announcer inspector do... "registry inspect." 3. In that SubscriptionRegistry inspector monitor the 'subscriptions' ivar for subsequent steps. * 'subscription' is initially an empty IdentitySet. 4. In the Announcer inspector do... "self open" * window "Spy: an Announcer" appears * 'subscriptions' now contains one AnnouncementSubscription 5. In the Announcer inspector again do... "self open" * another window "Spy: an Announcer" appears * 'subscriptions' now contains two AnnouncementSubscription 6. Close both Spy windows * 'subscriptions' still contains two AnnouncementSubscription Is the result of step 6 expected and/or desired? Intuitively I would expect 'subscriptions' to be empty. Doing "Smalltalk garbageCollect" has no effect. cheers -ben