diff --git a/backend/migrations/Version20260320111539.php b/backend/migrations/Version20260320111539.php
new file mode 100644
index 00000000..6baa0f40
--- /dev/null
+++ b/backend/migrations/Version20260320111539.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+final class Version20260320111539 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Fixes dkim_selector uniqueness';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE domains ADD CONSTRAINT domains_domain_dkim_selector_key UNIQUE (domain, dkim_selector)');
+        $this->addSql('ALTER TABLE domains DROP CONSTRAINT domains_dkim_selector_key');
+    }
+
+    public function down(Schema $schema): void
+    {
+        // this down() migration is auto-generated, please modify it to your needs
+
+    }
+}