diff --git a/dlt-database/entity/0003-refactor_transaction_recipe/BackendTransaction.ts b/dlt-database/entity/0003-refactor_transaction_recipe/BackendTransaction.ts
index 12b9c83cf..89dd3dbb0 100644
--- a/dlt-database/entity/0003-refactor_transaction_recipe/BackendTransaction.ts
+++ b/dlt-database/entity/0003-refactor_transaction_recipe/BackendTransaction.ts
@@ -9,8 +9,8 @@ export class BackendTransaction extends BaseEntity {
   @PrimaryGeneratedColumn('increment', { unsigned: true, type: 'bigint' })
   id: number
 
-  @Column({ name: 'backend_transaction_id', type: 'bigint', unsigned: true, nullable: true })
-  backendTransactionId?: number
+  @Column({ name: 'backend_transaction_id', type: 'bigint', unsigned: true, unique: true })
+  backendTransactionId: number
 
   @ManyToOne(() => Transaction, (transaction) => transaction.backendTransactions)
   @JoinColumn({ name: 'transaction_id' })
diff --git a/dlt-database/migrations/0003-refactor_transaction_recipe.ts b/dlt-database/migrations/0003-refactor_transaction_recipe.ts
index a3e8265e7..ac427cd21 100644
--- a/dlt-database/migrations/0003-refactor_transaction_recipe.ts
+++ b/dlt-database/migrations/0003-refactor_transaction_recipe.ts
@@ -72,6 +72,7 @@ export async function upgrade(queryFn: (query: string, values?: any[]) => Promis
         \`confirmed_at\` DATETIME NULL DEFAULT NULL,
         \`verifiedOnBackend\` TINYINT NOT NULL DEFAULT 0,
         PRIMARY KEY (\`id\`),
+        UNIQUE (\`backend_transaction_id\`),
         FOREIGN KEY (\`transaction_id\`) REFERENCES transactions(id)
       ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
       `,