diff --git a/roles/matrix-dendrite/tasks/register_user.yml b/roles/matrix-dendrite/tasks/register_user.yml
index e1b974825..d37e633bf 100644
--- a/roles/matrix-dendrite/tasks/register_user.yml
+++ b/roles/matrix-dendrite/tasks/register_user.yml
@@ -9,6 +9,11 @@
     msg: "The `password` variable needs to be provided to this playbook, via --extra-vars"
   when: "password is not defined or password == '<your-password>'"
 
+- name: Fail if playbook called incorrectly
+  ansible.builtin.fail:
+    msg: "The `admin` variable needs to be provided to this playbook, via --extra-vars"
+  when: "admin is not defined or admin not in ['yes', 'no']"
+
 - name: Ensure matrix-dendrite is started
   ansible.builtin.service:
     name: matrix-dendrite
@@ -23,6 +28,6 @@
 
 - name: Register user
   ansible.builtin.command:
-    cmd: "{{ matrix_local_bin_path }}/matrix-dendrite-create-account {{ username | quote }} {{ password | quote }}"
+    cmd: "{{ matrix_local_bin_path }}/matrix-dendrite-create-account {{ username | quote }} {{ password | quote }} {{ '1' if admin == 'yes' else '0' }}"
   register: matrix_dendrite_register_user_result
   changed_when: matrix_dendrite_register_user_result.rc == 0