diff --git a/devtools/deployments/opencloud_full/.env b/devtools/deployments/opencloud_full/.env
index 39e940fab3..fe94283028 100644
--- a/devtools/deployments/opencloud_full/.env
+++ b/devtools/deployments/opencloud_full/.env
@@ -312,6 +312,12 @@ KEYCLOAK_ADMIN_PASSWORD=
 # Defaults to "stalwart.opencloud.test"
 STALWART_DOMAIN=
 
+# LDAP configuration to use for Stalwart:
+# Can either be either
+# - idmldap: for the built-in IDP/IDM
+# - ldap: when using KeyCloak and OpenLDAP
+STALWART_AUTH_DIRECTORY=idmldap
+
 ## IMPORTANT ##
 # This MUST be the last line as it assembles the supplemental compose files to be used.
 # ALL supplemental configs must be added here, whether commented or not.