diff --git a/roles/matrix-postgres/defaults/main.yml b/roles/matrix-postgres/defaults/main.yml
index ad417e0b..89559f5d 100644
--- a/roles/matrix-postgres/defaults/main.yml
+++ b/roles/matrix-postgres/defaults/main.yml
@@ -42,3 +42,9 @@ matrix_postgres_container_postgres_bind_port: ""
 #     username: matrix_appservice_slack
 #     password: some_password
 matrix_postgres_additional_databases: []
+
+# The number of seconds to wait after starting `matrix-postgres.service`
+# and before trying to run queries for creating additional databases/users against it.
+#
+# For most (subsequent) runs, Postgres would already be running, so no waiting will be happening at all.
+matrix_postgres_additional_databases_postgres_start_wait_timeout_seconds: 15
diff --git a/roles/matrix-postgres/tasks/util/create_additional_databases.yml b/roles/matrix-postgres/tasks/util/create_additional_databases.yml
index 51deb228..0ad460dd 100644
--- a/roles/matrix-postgres/tasks/util/create_additional_databases.yml
+++ b/roles/matrix-postgres/tasks/util/create_additional_databases.yml
@@ -1,10 +1,20 @@
 ---
 
-# TODO - we should ensure matrix-postgres.service is started.
-# .. and that if we had just started it, we've given it ample time to initialize,
-# before we attempt to run queries against it.
+- name: Ensure matrix-postgres is started
+  service:
+    name: matrix-postgres
+    state: started
+    daemon_reload: yes
+  register: matrix_postgres_service_start_result
 
-- name: Create additional Postgers user and database
+- name: Wait a bit, so that Postgres can start
+  wait_for:
+    timeout: "{{ matrix_postgres_additional_databases_postgres_start_wait_timeout_seconds }}"
+  delegate_to: 127.0.0.1
+  become: false
+  when: "matrix_postgres_service_start_result.changed|bool"
+
+- name: Create additional Postgres user and database
   include_tasks: "{{ role_path }}/tasks/util/create_additional_database.yml"
   with_items: "{{ matrix_postgres_additional_databases }}"
   loop_control: