diff --git a/addons/mail/static/tests/discuss_tests.js b/addons/mail/static/tests/discuss_tests.js
index 8e8b663e83f..1e269ca7074 100644
--- a/addons/mail/static/tests/discuss_tests.js
+++ b/addons/mail/static/tests/discuss_tests.js
@@ -1818,8 +1818,16 @@ QUnit.test('messages marked as read move to "History" mailbox', async function (
     discuss.destroy();
 });
 
- QUnit.test('all messages in "Inbox" in "History" after marked all as read', async function (assert) {
-    assert.expect(10)
+QUnit.test('all messages in "Inbox" in "History" after marked all as read', async function (assert) {
+    /**
+     * FIXME: for some reasons, this test may crash non-deterministically on
+     * runbot around once every hundreds of builds. As of the writing of this
+     * comment, no explanation has been found, so extra `nextTick()` have been
+     * added in the meantime. This work-around sucks, but this is better than
+     * skipping this test, until we find the issue and fix it properly in the
+     * future.
+     */
+    assert.expect(10);
 
     const messagesData = [];
     for (let i = 0; i < 40; i++) {
@@ -1898,6 +1906,16 @@ QUnit.test('messages marked as read move to "History" mailbox', async function (
 
     const $history = discuss.$('.o_mail_discuss_item[data-thread-id="mailbox_history"]');
     await testUtils.dom.click($history);
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
     assert.verifySteps(['message_fetch'],
         "should fetch messages once for history");
     assert.containsN(discuss, '.o_thread_message', 30,
@@ -1907,6 +1925,16 @@ QUnit.test('messages marked as read move to "History" mailbox', async function (
     discuss.$('.o_mail_thread').scrollTop(0);
     await loadMoreDef;
     await testUtils.nextTick();
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
+    await testUtils.nextTick(); // extra (non-deterministic)
     assert.verifySteps(['message_fetch'],
         "should fetch more messages in history for loadMore");
     assert.containsN(discuss, '.o_thread_message', 40,