diff --git a/setup/flavors/compose/mailu.env b/setup/flavors/compose/mailu.env
index 150c70a3..4dce34f1 100644
--- a/setup/flavors/compose/mailu.env
+++ b/setup/flavors/compose/mailu.env
@@ -176,6 +176,7 @@ DB_NAME={{ db_name }}
 {% endif %}
 
 {% if (postgresql == 'external' or db_flavor == 'mysql') and webmail_type == 'roundcube' %}
+ROUNDCUBE_DB_FLAVOR={{ db_flavor }}
 ROUNDCUBE_DB_USER={{ roundcube_db_user }}
 ROUNDCUBE_DB_PW={{ roundcube_db_pw }}
 ROUNDCUBE_DB_HOST={{ roundcube_db_url }}