diff --git a/tests/unit/test_multi_driver.py b/tests/unit/test_multi_driver.py
index 89ab219f92..e59b50e192 100644
--- a/tests/unit/test_multi_driver.py
+++ b/tests/unit/test_multi_driver.py
@@ -20,6 +20,12 @@ class TestGerritAndGithub(ZuulTestCase):
     config_file = 'zuul-connections-gerrit-and-github.conf'
     tenant_config_file = 'config/multi-driver/main.yaml'
 
+    # Those tests are also using the fake github implementation which
+    # means that every scheduler gets a different fake github instance.
+    # Thus, assertions might fail depending on which scheduler did the
+    # interaction with Github.
+    scheduler_count = 1
+
     def test_multiple_project_gerrit_and_github(self):
         self.executor_server.hold_jobs_in_build = True
 
diff --git a/tests/unit/test_pagure_driver.py b/tests/unit/test_pagure_driver.py
index 5d18e2eace..dccfb92e01 100644
--- a/tests/unit/test_pagure_driver.py
+++ b/tests/unit/test_pagure_driver.py
@@ -973,6 +973,12 @@ class TestGithubToPagureCRD(ZuulTestCase):
     config_file = 'zuul-crd-pagure.conf'
     tenant_config_file = 'config/cross-source-pagure/github.yaml'
 
+    # Those tests are also using the fake github implementation which
+    # means that every scheduler gets a different fake github instance.
+    # Thus, assertions might fail depending on which scheduler did the
+    # interaction with Github.
+    scheduler_count = 1
+
     def test_crd_gate(self):
         "Test cross-repo dependencies"
         A = self.fake_github.openFakePullRequest('github/project1', 'master',
diff --git a/tests/unit/test_v3.py b/tests/unit/test_v3.py
index 90fe02a344..c1454eef3a 100644
--- a/tests/unit/test_v3.py
+++ b/tests/unit/test_v3.py
@@ -3267,6 +3267,11 @@ class TestJobContamination(AnsibleZuulTestCase):
 
     config_file = 'zuul-connections-gerrit-and-github.conf'
     tenant_config_file = 'config/zuul-job-contamination/main.yaml'
+    # Those tests are also using the fake github implementation which
+    # means that every scheduler gets a different fake github instance.
+    # Thus, assertions might fail depending on which scheduler did the
+    # interaction with Github.
+    scheduler_count = 1
 
     def test_job_contamination_playbooks(self):
         conf = textwrap.dedent(