diff --git a/roles/mailman/defaults/main.yml b/roles/mailman/defaults/main.yml
index 6fb905b432..dffdecd16e 100644
--- a/roles/mailman/defaults/main.yml
+++ b/roles/mailman/defaults/main.yml
@@ -1,6 +1,6 @@
 ---
 mailman_webui_basedir: /srv/webui
-mailman_webui_confdir: ${mailman_webui_basedir}/config
+mailman_webui_confdir: "{{ mailman_webui_basedir }}/config"
 mailman_dbserver: localhost
 mailman_postfix_mydestination: "{{ ansible_fqdn }}"
 mailman_mm_db_pass: changeme