diff --git a/roles/mailserver_database/templates/tables.sql.j2 b/roles/mailserver_database/templates/tables.sql.j2
index 800377d..4ddc3f7 100644
--- a/roles/mailserver_database/templates/tables.sql.j2
+++ b/roles/mailserver_database/templates/tables.sql.j2
@@ -24,14 +24,15 @@ INSERT INTO virtual_users (domain_id, email, password, quota) VALUES (
 CREATE TABLE IF NOT EXISTS virtual_aliases (
     id integer primary key generated by default as identity,
     domain_id integer NOT NULL,
-    source varchar(254) NOT NULL UNIQUE,
+    source varchar(254) NOT NULL,
     destination varchar(254) NOT NULL,
     FOREIGN KEY (domain_id) REFERENCES virtual_domains(id) ON DELETE CASCADE
 );
+CREATE UNIQUE INDEX IF NOT EXISTS virtual_aliases_s_d_key ON virtual_aliases (source, destination);
 {% for alias in mailserver_database.virtual_aliases %}
 INSERT INTO virtual_aliases (domain_id, source, destination) VALUES (
     (SELECT id FROM virtual_domains WHERE name = '{{ virtual_domain }}'),
     '{{ alias.source }}@{{ virtual_domain }}',
     '{{ alias.destination }}@{{ virtual_domain }}'
-) ON CONFLICT (source) DO UPDATE SET destination = EXCLUDED.destination;
+) ON CONFLICT (source, destination) DO NOTHING;
 {% endfor %}