diff --git a/roles/matrix-base/tasks/main.yml b/roles/matrix-base/tasks/main.yml
index a1bb6754..26e01996 100644
--- a/roles/matrix-base/tasks/main.yml
+++ b/roles/matrix-base/tasks/main.yml
@@ -2,6 +2,11 @@
   tags:
     - always
 
+- import_tasks: "{{ role_path }}/tasks/validate_config.yml"
+  when: "run_setup|bool"
+  tags:
+    - setup-all
+
 - import_tasks: "{{ role_path }}/tasks/clean_up_old_files.yml"
   when: run_setup|bool
   tags:
diff --git a/roles/matrix-base/tasks/validate_config.yml b/roles/matrix-base/tasks/validate_config.yml
new file mode 100644
index 00000000..3ea1f5a1
--- /dev/null
+++ b/roles/matrix-base/tasks/validate_config.yml
@@ -0,0 +1,11 @@
+---
+
+- name: (Deprecation) Warn about unused user/group variables
+  fail:
+    msg: >
+      The `{{ item }}` variable defined in your configuration is not used by this playbook anymore.
+      User/group creation is now dynamic. You can remove these variables from your configuration, as they have no effect on anything.
+  when: "item in vars"
+  with_items:
+    - 'matrix_user_uid'
+    - 'matrix_user_uid'