diff --git a/roles/custom/matrix-bridge-mautrix-slack/defaults/main.yml b/roles/custom/matrix-bridge-mautrix-slack/defaults/main.yml
index c2b5a159..ae03943a 100644
--- a/roles/custom/matrix-bridge-mautrix-slack/defaults/main.yml
+++ b/roles/custom/matrix-bridge-mautrix-slack/defaults/main.yml
@@ -63,7 +63,7 @@ matrix_mautrix_slack_sqlite_database_path_in_container: "/data/mautrix-slack.db"
 
 matrix_mautrix_slack_database_username: 'matrix_mautrix_slack'
 matrix_mautrix_slack_database_password: 'some-password'
-matrix_mautrix_slack_database_hostname: 'matrix-postgres'
+matrix_mautrix_slack_database_hostname: ''
 matrix_mautrix_slack_database_port: 5432
 matrix_mautrix_slack_database_name: 'matrix_mautrix_slack'
 
diff --git a/roles/custom/matrix-bridge-mautrix-slack/tasks/validate_config.yml b/roles/custom/matrix-bridge-mautrix-slack/tasks/validate_config.yml
index 363bbacf..3c764a4e 100644
--- a/roles/custom/matrix-bridge-mautrix-slack/tasks/validate_config.yml
+++ b/roles/custom/matrix-bridge-mautrix-slack/tasks/validate_config.yml
@@ -1,13 +1,14 @@
 ---
 
-- name: Fail if required settings not defined
+- name: Fail if required mautrix-slack settings not defined
   ansible.builtin.fail:
     msg: >-
-      You need to define a required configuration setting (`{{ item }}`).
-  when: "vars[item] == ''"
+      You need to define a required configuration setting (`{{ item.name }}`).
+  when: "item.when | bool and vars[item.name] == ''"
   with_items:
-    - "matrix_mautrix_slack_appservice_token"
-    - "matrix_mautrix_slack_homeserver_token"
+    - {'name': 'matrix_mautrix_slack_appservice_token', when: true}
+    - {'name': 'matrix_mautrix_slack_homeserver_token', when: true}
+    - {'name': 'matrix_mautrix_slack_database_hostname', when: "{{ matrix_mautrix_slack_database_engine == 'postgres' }}"}
 
 - name: Fail if appservice-slack and mautrix-slack have conflicting bot usernames
   when: matrix_appservice_slack_enabled | default(False) | bool and matrix_mautrix_slack_appservice_bot_username == matrix_appservice_slack_bot_name | default ('')