--- a/netwerk/protocol/http/nsHttpHandler.cpp
+++ b/netwerk/protocol/http/nsHttpHandler.cpp
@@ -360,16 +360,18 @@ nsHttpHandler::Init()
     if (obsService) {
         // register the handler object as a weak callback as we don't need to worry
         // about shutdown ordering.
         obsService->AddObserver(this, "profile-change-net-teardown", true);
         obsService->AddObserver(this, "profile-change-net-restore", true);
         obsService->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, true);
         obsService->AddObserver(this, "net:clear-active-logins", true);
         obsService->AddObserver(this, "net:prune-dead-connections", true);
+        // Sent by the TorButton add-on in the Tor Browser
+        obsService->AddObserver(this, "net:prune-all-connections", true);
         obsService->AddObserver(this, "net:failed-to-process-uri-content", true);
         obsService->AddObserver(this, "last-pb-context-exited", true);
         obsService->AddObserver(this, "webapps-clear-data", true);
         obsService->AddObserver(this, "browser:purge-session-history", true);
         obsService->AddObserver(this, NS_NETWORK_LINK_TOPIC, true);
         obsService->AddObserver(this, "application-background", true);
     }
 
@@ -2039,16 +2041,21 @@ nsHttpHandler::Observe(nsISupports *subj
         InitConnectionMgr();
     } else if (!strcmp(topic, "net:clear-active-logins")) {
         mAuthCache.ClearAll();
         mPrivateAuthCache.ClearAll();
     } else if (!strcmp(topic, "net:prune-dead-connections")) {
         if (mConnMgr) {
             mConnMgr->PruneDeadConnections();
         }
+    } else if (!strcmp(topic, "net:prune-all-connections")) {
+        if (mConnMgr) {
+            mConnMgr->DoShiftReloadConnectionCleanup(nullptr);
+            mConnMgr->PruneDeadConnections();
+        }
     } else if (!strcmp(topic, "net:failed-to-process-uri-content")) {
         nsCOMPtr<nsIURI> uri = do_QueryInterface(subject);
         if (uri && mConnMgr) {
             mConnMgr->ReportFailedToProcess(uri);
         }
     } else if (!strcmp(topic, "last-pb-context-exited")) {
         mPrivateAuthCache.ClearAll();
         if (mConnMgr) {