diff --git a/extension/js/content_scripts/webmail/gmail-element-replacer.ts b/extension/js/content_scripts/webmail/gmail-element-replacer.ts
index aa9e1d652c7..9098da46e64 100644
--- a/extension/js/content_scripts/webmail/gmail-element-replacer.ts
+++ b/extension/js/content_scripts/webmail/gmail-element-replacer.ts
@@ -472,8 +472,9 @@ export class GmailElementReplacer implements WebmailElementReplacer {
     } else if (method === 'append') {
       if (replace) {
         const parent = msgBody.parent();
-        msgBody.replaceWith(this.wrapMsgBodyEl(msgBody.html() + newHtmlContent_MUST_BE_XSS_SAFE)); // xss-reinsert // xss-safe-value
-        this.ensureHasParentNode(msgBody); // Gmail is using msgBody.parentNode (#2271)
+        const wrapper = msgBody.wrap(this.wrapMsgBodyEl(''));
+        wrapper.append(newHtmlContent_MUST_BE_XSS_SAFE); // xss-reinsert // xss-safe-value
+        this.ensureHasParentNode(wrapper); // Gmail is using msgBody.parentNode (#2271)
         return parent.find('.message_inner_body'); // need to return new selector - old element was replaced
       } else {
         return msgBody.append(newHtmlContent_MUST_BE_XSS_SAFE); // xss-safe-value
diff --git a/test/source/browser/controllable.ts b/test/source/browser/controllable.ts
index 92699ae76a1..19ee4912407 100644
--- a/test/source/browser/controllable.ts
+++ b/test/source/browser/controllable.ts
@@ -528,7 +528,8 @@ export class ControllablePage extends ControllableBase {
     try {
       await this.page.waitForNavigation({ timeout: seconds * 1000 });
     } catch (e) {
-      if (e.message.indexOf('Navigation Timeout Exceeded') === 0) {
+      // can be "Navigation Timeout Exceeded" or "Navigation timeout of 5000 ms exceeded"
+      if (new RegExp('^Navigation timeout .*xceeded$').test(e.message)) {
         return;
       }
       throw e;
diff --git a/test/source/tests/gmail.ts b/test/source/tests/gmail.ts
index e3c50710278..4aad51b6c2e 100644
--- a/test/source/tests/gmail.ts
+++ b/test/source/tests/gmail.ts
@@ -148,6 +148,26 @@ export const defineGmailTests = (testVariant: TestVariant, testWithBrowser: Test
       await pageHasSecureReplyContainer(t, browser, gmailPage);
     }));
 
+    ava.default('mail.google.com - Thunderbird signature [html] is recognized', testWithBrowser('ci.tests.gmail', async (t, browser) => {
+      const gmailPage = await openGmailPage(t, browser, '/FMfcgxwKjBRGVhcgRwklplhBCCKgSdfk');
+      const urls = await gmailPage.getFramesUrls(['/chrome/elements/pgp_block.htm'], { sleep: 10, appearIn: 20 });
+      expect(urls.length).to.equal(1);
+      const url = urls[0].split('/chrome/elements/pgp_block.htm')[1];
+      const signature = ['Dhartley@Verdoncollege.School.Nz', 'matching signature'];
+      await BrowserRecipe.pgpBlockVerifyDecryptedContent(t, browser, { params: url, content: ['1234'], signature });
+      await pageHasSecureReplyContainer(t, browser, gmailPage);
+    }));
+
+    ava.default('mail.google.com - Thunderbird signature [plain] is recognized', testWithBrowser('ci.tests.gmail', async (t, browser) => {
+      const gmailPage = await openGmailPage(t, browser, '/FMfcgxwKjBTWTbDjXSJVjDjKlWJGbWQd');
+      const urls = await gmailPage.getFramesUrls(['/chrome/elements/pgp_block.htm'], { sleep: 10, appearIn: 20 });
+      expect(urls.length).to.equal(1);
+      const url = urls[0].split('/chrome/elements/pgp_block.htm')[1];
+      const signature = ['Dhartley@Verdoncollege.School.Nz', 'matching signature'];
+      await BrowserRecipe.pgpBlockVerifyDecryptedContent(t, browser, { params: url, content: ['1234'], signature });
+      await pageHasSecureReplyContainer(t, browser, gmailPage);
+    }));
+
     ava.default('mail.google.com - secure reply btn accepts reply prompt', testWithBrowser('ci.tests.gmail', async (t, browser) => {
       const gmailPage = await openGmailPage(t, browser, '/FMfcgxwJXVGtMJwQTZmBDlspVWDvsnnL'); // encrypted convo
       await Util.sleep(5);