diff --git a/plinth/modules/i2p/tests/test_functional.py b/plinth/modules/i2p/tests/test_functional.py
index c3e2c0a11..d71a5f7ef 100644
--- a/plinth/modules/i2p/tests/test_functional.py
+++ b/plinth/modules/i2p/tests/test_functional.py
@@ -14,3 +14,4 @@ class TestI2pApp(BaseAppTests):
     app_name = 'i2p'
     has_service = True
     has_web = True
+    diagnostics_delay = 1
diff --git a/plinth/modules/matrixsynapse/tests/test_functional.py b/plinth/modules/matrixsynapse/tests/test_functional.py
index 893593ea9..4d844fefd 100644
--- a/plinth/modules/matrixsynapse/tests/test_functional.py
+++ b/plinth/modules/matrixsynapse/tests/test_functional.py
@@ -4,7 +4,6 @@ Functional, browser based tests for matrixsynapse app.
 """
 
 import pytest
-import time
 
 from plinth.tests import functional
 
@@ -15,6 +14,7 @@ class TestMatrixSynapseApp(functional.BaseAppTests):
     app_name = 'matrixsynapse'
     has_service = True
     has_web = False
+    diagnostics_delay = 1
 
     @pytest.fixture(scope='class', autouse=True)
     def fixture_setup(self, session_browser):
@@ -24,8 +24,3 @@ class TestMatrixSynapseApp(functional.BaseAppTests):
         functional.install(session_browser, self.app_name)
         functional.app_select_domain_name(session_browser, self.app_name,
                                           'mydomain.example')
-
-    def test_run_diagnostics(self, session_browser):
-        """Add a short delay before checking diagnostics."""
-        time.sleep(1)
-        super().test_run_diagnostics(session_browser)
diff --git a/plinth/tests/functional/__init__.py b/plinth/tests/functional/__init__.py
index 7d4f8e2a0..acee59ca7 100644
--- a/plinth/tests/functional/__init__.py
+++ b/plinth/tests/functional/__init__.py
@@ -599,6 +599,7 @@ class BaseAppTests:
     has_service = False
     has_web = True
     check_diagnostics = True
+    diagnostics_delay = 0
 
     def assert_app_running(self, session_browser):
         """Assert that the app is running."""
@@ -639,6 +640,7 @@ class BaseAppTests:
         if not self.check_diagnostics:
             pytest.skip(f'Skipping diagnostics check for ${self.app_name}.')
 
+        time.sleep(self.diagnostics_delay)
         session_browser.find_by_id('id_extra_actions_button').click()
         submit(session_browser, form_class='form-diagnostics-button')