Steps to reproduce: - Create a new profile - Set home page to about:downloads - Set to restore tabs and windows when Firefox starts The issue can also occur with existing profiles from older Firefox versions that use these settings. Since Firefox 55, session restore will fail with these settings; I usually get an empty tab for each tab that was supposed to be restored instead. There seem to be additional factors affecting this, as I was also somehow able to get Firefox into a state where I couldn't reprocude the issue anymore, even though the same settings were still set. The following error message is printed on the console: > A coding exception was thrown in a Promise resolution callback. > See https://developer.mozilla.org/Mozilla/JavaScript_code_modules/Promise.jsm/Promise > > Full message: TypeError: access to strict mode caller function is censored > Full stack: NS_ASSERT@resource://gre/modules/debug.js:50:7 > restoreTab@resource:///modules/sessionstore/SessionStore.jsm:3552:5 > restoreTabs@resource:///modules/sessionstore/SessionStore.jsm:3539:7 > ssi_restoreWindow@resource:///modules/sessionstore/SessionStore.jsm:3404:7 > ssi_restoreWindows@resource:///modules/sessionstore/SessionStore.jsm:3484:5 > initializeWindow@resource:///modules/sessionstore/SessionStore.jsm:1158:11 > onBeforeBrowserWindowShown/<@resource:///modules/sessionstore/SessionStore.jsm:1307:9 > process@resource://gre/modules/Promise-backend.js:922:23 > walkerLoop@resource://gre/modules/Promise-backend.js:806:7 > scheduleWalkerLoop/<@resource://gre/modules/Promise-backend.js:742:11 SessionStore.jsm:3552:5 seems to refer to the assert at the beginning of restoreTab(): > NS_ASSERT(!tab.linkedBrowser.__SS_restoreState, > "must reset tab before calling restoreTab()"); Workaround: Use a different home page.

may be duplication of Bug 1388628