diff --git a/browser/components/about/AboutRedirector.cpp b/browser/components/about/AboutRedirector.cpp
index be2b503f6414..239562d3e167 100644
--- a/browser/components/about/AboutRedirector.cpp
+++ b/browser/components/about/AboutRedirector.cpp
@@ -22,6 +22,7 @@ namespace browser {
 NS_IMPL_ISUPPORTS(AboutRedirector, nsIAboutModule)
 
 bool AboutRedirector::sUseOldPreferences = false;
+bool AboutRedirector::sActivityStreamEnabled = false;
 
 struct RedirEntry {
   const char* id;
@@ -206,8 +207,26 @@ AboutRedirector::GetURIFlags(nsIURI *aURI, uint32_t *result)
 
   nsAutoCString name = GetAboutModuleName(aURI);
 
+  static bool sASEnabledCacheInited = false;
+  if (!sASEnabledCacheInited) {
+    Preferences::AddBoolVarCache(&sActivityStreamEnabled,
+                                 "browser.newtabpage.activity-stream.enabled");
+    sASEnabledCacheInited = true;
+  }
+
   for (auto & redir : kRedirMap) {
     if (name.Equals(redir.id)) {
+
+      // Once ActivityStream is fully rolled out and we've removed Tiles,
+      // this special case can go away and the flag can just become part
+      // of the normal about:newtab entry in kRedirMap.
+      if (name.EqualsLiteral("newtab")) {
+        if (sActivityStreamEnabled) {
+          *result = redir.flags | nsIAboutModule::URI_MUST_LOAD_IN_CHILD;
+          return NS_OK;
+        }
+      }
+
       *result = redir.flags;
       return NS_OK;
     }
diff --git a/browser/components/about/AboutRedirector.h b/browser/components/about/AboutRedirector.h
index eaf25e3400a9..885302522db5 100644
--- a/browser/components/about/AboutRedirector.h
+++ b/browser/components/about/AboutRedirector.h
@@ -27,6 +27,7 @@ protected:
 
 private:
   static bool sUseOldPreferences;
+  static bool sActivityStreamEnabled;
 };
 
 } // namespace browser
diff --git a/browser/components/about/moz.build b/browser/components/about/moz.build
index a1556825b1ab..4f14bc5a92a0 100644
--- a/browser/components/about/moz.build
+++ b/browser/components/about/moz.build
@@ -11,6 +11,8 @@ EXPORTS.mozilla.browser += [
     'AboutRedirector.h',
 ]
 
+XPCSHELL_TESTS_MANIFESTS += ['test/unit/xpcshell.ini']
+
 SOURCES += [
     'AboutRedirector.cpp',
 ]
diff --git a/browser/components/about/test/unit/test_getURIFlags.js b/browser/components/about/test/unit/test_getURIFlags.js
new file mode 100644
index 000000000000..c28fa09facfb
--- /dev/null
+++ b/browser/components/about/test/unit/test_getURIFlags.js
@@ -0,0 +1,33 @@
+const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
+
+Cu.import("resource://gre/modules/Services.jsm");
+
+const contract = "@mozilla.org/network/protocol/about;1?what=newtab";
+const am = Cc[contract].getService(Ci.nsIAboutModule);
+const uri = Services.io.newURI("about:newtab");
+
+function run_test() {
+  test_AS_enabled_flags();
+  test_AS_disabled_flags();
+}
+
+// Since tiles isn't e10s capable, it shouldn't advertise that it can load in
+// the child.
+function test_AS_disabled_flags() {
+  Services.prefs.setBoolPref("browser.newtabpage.activity-stream.enabled",
+    false);
+
+  let flags = am.getURIFlags(uri);
+
+  ok(!(flags & Ci.nsIAboutModule.URI_MUST_LOAD_IN_CHILD));
+}
+
+// Activity Stream, however, is e10s-capable, and should advertise it.
+function test_AS_enabled_flags() {
+  Services.prefs.setBoolPref("browser.newtabpage.activity-stream.enabled",
+    true);
+
+  let flags = am.getURIFlags(uri);
+
+  ok(flags & Ci.nsIAboutModule.URI_MUST_LOAD_IN_CHILD);
+}
diff --git a/browser/components/about/test/unit/xpcshell.ini b/browser/components/about/test/unit/xpcshell.ini
new file mode 100644
index 000000000000..4fcef61417bf
--- /dev/null
+++ b/browser/components/about/test/unit/xpcshell.ini
@@ -0,0 +1,6 @@
+[DEFAULT]
+head =
+# make the firefox services (eg newtab-service) available to xpcshell
+firefox-appdir = browser
+
+[test_getURIFlags.js]
diff --git a/browser/components/sessionstore/test/browser_background_tab_crash.js b/browser/components/sessionstore/test/browser_background_tab_crash.js
index f0dfa5ac0e15..bd66b94d265b 100644
--- a/browser/components/sessionstore/test/browser_background_tab_crash.js
+++ b/browser/components/sessionstore/test/browser_background_tab_crash.js
@@ -242,12 +242,7 @@ add_task(async function test_preload_crash() {
   // Create a fresh preloaded browser
   gBrowser._createPreloadBrowser();
 
-  // XXX Temporarily disabled until bug 1365643 relands.  At that time, this
-  // this statement, as well as the eslint-disable-line below, should be
-  // removed.
-  return;
-
-  await BrowserTestUtils.crashBrowser(gBrowser._preloadedBrowser, false); // eslint-disable-line no-unreachable
+  await BrowserTestUtils.crashBrowser(gBrowser._preloadedBrowser, false);
 
   Assert.ok(!gBrowser._preloadedBrowser);
 });