diff --git a/uriloader/exthandler/tests/mochitest/browser_auto_close_window.js b/uriloader/exthandler/tests/mochitest/browser_auto_close_window.js
index 374b957fc0df..ab00f16f367e 100644
--- a/uriloader/exthandler/tests/mochitest/browser_auto_close_window.js
+++ b/uriloader/exthandler/tests/mochitest/browser_auto_close_window.js
@@ -57,23 +57,31 @@ add_task(async function simple_navigation() {
   });
 });
 
+// Given a browser pointing to download_page.html, clicks on the link that
+// opens with target="_blank" (i.e. a new tab) and ensures that we
+// automatically open and close that tab.
+async function testNewTab(browser) {
+  let targetURL = browser.currentURI.spec;
+  let dialogAppeared = promiseHelperAppDialog();
+  let tabOpened = BrowserTestUtils.waitForEvent(gBrowser.tabContainer, "TabOpen").then((event) => {
+    return [ event.target, BrowserTestUtils.tabRemoved(event.target) ];
+  });
+
+  await BrowserTestUtils.synthesizeMouseAtCenter("#target_blank", {}, browser);
+
+  let windowContext = await dialogAppeared;
+  is(windowContext.gBrowser.selectedBrowser.currentURI.spec, targetURL,
+     "got the right windowContext");
+  let [ tab, closed ] = await tabOpened;
+  await closed;
+  is(tab.linkedBrowser, null, "tab was opened and closed");
+}
+
 add_task(async function target_blank() {
   // Tests that a link with target=_blank opens a new tab and closes it,
   // returning the window that we're using for navigation.
   await BrowserTestUtils.withNewTab({ gBrowser, url: URL }, async function(browser) {
-    let dialogAppeared = promiseHelperAppDialog();
-    let tabOpened = BrowserTestUtils.waitForEvent(gBrowser.tabContainer, "TabOpen").then((event) => {
-      return [ event.target, BrowserTestUtils.tabRemoved(event.target) ];
-    });
-
-    await BrowserTestUtils.synthesizeMouseAtCenter("#target_blank", {}, browser);
-
-    let windowContext = await dialogAppeared;
-    is(windowContext.gBrowser.selectedBrowser.currentURI.spec, URL,
-       "got the right windowContext");
-    let [ tab, closed ] = await tabOpened;
-    await closed;
-    is(tab.linkedBrowser, null, "tab was opened and closed");
+    await testNewTab(browser);
   });
 });
 
@@ -99,6 +107,25 @@ add_task(async function new_window() {
   });
 });
 
+add_task(async function nested_window_opens() {
+  // Tests that the window auto-closing feature works if the download is
+  // initiated by a window that, itself, has an opener (see bug 1373109).
+  await BrowserTestUtils.withNewTab({ gBrowser, url: URL }, async function(outerBrowser) {
+    BrowserTestUtils.synthesizeMouseAtCenter("#open_in_new_tab", {}, outerBrowser);
+    let secondTab = await BrowserTestUtils.waitForNewTab(gBrowser, null, true);
+    let nestedBrowser = secondTab.linkedBrowser;
+
+    await ContentTask.spawn(nestedBrowser, null, function() {
+      ok(content.opener, "this window has an opener");
+    });
+
+    await testNewTab(nestedBrowser);
+
+    isnot(secondTab.linkedBrowser, null, "the page that triggered the download is still open");
+    await BrowserTestUtils.removeTab(secondTab);
+  });
+});
+
 add_task(async function cleanup() {
   // Unregister our factory from XPCOM and restore the original CID.
   registrar.unregisterFactory(MOCK_HELPERAPP_DIALOG_CID, mockHelperAppService);
diff --git a/uriloader/exthandler/tests/mochitest/download_page.html b/uriloader/exthandler/tests/mochitest/download_page.html
index 3f482cd238ab..f02380f854c5 100644
--- a/uriloader/exthandler/tests/mochitest/download_page.html
+++ b/uriloader/exthandler/tests/mochitest/download_page.html
@@ -15,4 +15,5 @@
   <a href="download.bin" id="regular_load">regular load</a>
   <a href="download.bin" id="target_blank" target="_blank">target blank</a>
   <a href="#" onclick="launch_download(); return false" id="new_window">new window</a>
+  <a href="#" onclick="window.open('download_page.html?newwin'); return false" id="open_in_new_tab">click to reopen</a>
 </body>