diff --git a/playbooks/roles/install-ansible/tasks/main.yaml b/playbooks/roles/install-ansible/tasks/main.yaml
index 31119d5f74..65b9d03e93 100644
--- a/playbooks/roles/install-ansible/tasks/main.yaml
+++ b/playbooks/roles/install-ansible/tasks/main.yaml
@@ -32,6 +32,23 @@
     _install_ansible_from_devel: true
   when: '"github.com/ansible/ansible" in install_ansible_name'
 
+# Since ~2020-11 ansible renamed "ansible-base" to "ansible-core".
+# Unfortunately, ansible-base and ansible-core can not live happily
+# together.  For testinfra, our tox role pre-installs the requirements
+# from tox.ini (ansible-base) but then tries to install siblings (the
+# checked out ansible tree, now trying to install the "ansible-core"
+# package).  There is no working "ansible-core" package on PyPi, so
+# for now we have to switch this out in the tox.ini for the -devel job
+# to work.  We can remove this when "ansible-core" is published at an
+# appropriate version on PyPi; at that point the checked-out tree can
+# override the package in the testing tox venv.
+- name: Override ansible-base tox install
+  when: '"github.com/ansible/ansible" in install_ansible_name'
+  lineinfile:
+    path: /home/zuul/src/opendev.org/opendev/system-config/tox.ini
+    regexp: '^  ansible-base # see install-ansible/tasks/main\.yaml$'
+    line:   '  ansible-core'
+
 - name: Setup Ansible stub for post 2.10 compat
   include_tasks: install_ansible_stub.yaml
   when: _install_ansible_from_devel is defined
diff --git a/tox.ini b/tox.ini
index 5aac2e1f36..e4334bebc1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -38,7 +38,7 @@ commands = sphinx-build -W -E -b html doc/source doc/build/html
 
 [testenv:testinfra]
 deps =
-  ansible-base
+  ansible-base # see install-ansible/tasks/main.yaml
   pytest-html # MPL-2.0
   pytest-testinfra>=6.0.0