diff --git a/src/DoctrineOutbox/DoctrineTransactionalMessageRepository.php b/src/DoctrineOutbox/DoctrineTransactionalMessageRepository.php
index 2c9a62c..00bf3b6 100644
--- a/src/DoctrineOutbox/DoctrineTransactionalMessageRepository.php
+++ b/src/DoctrineOutbox/DoctrineTransactionalMessageRepository.php
@@ -4,12 +4,14 @@
 
 use Doctrine\DBAL\Connection;
 use EventSauce\EventSourcing\AggregateRootId;
+use EventSauce\EventSourcing\Header;
 use EventSauce\EventSourcing\Message;
 use EventSauce\EventSourcing\MessageRepository;
 use EventSauce\EventSourcing\PaginationCursor;
 use EventSauce\EventSourcing\UnableToPersistMessages;
 use EventSauce\MessageOutbox\OutboxRepository;
 use Generator;
+use Ramsey\Uuid\Uuid;
 use Throwable;
 
 class DoctrineTransactionalMessageRepository implements MessageRepository
@@ -23,6 +25,12 @@ public function __construct(
     public function persist(Message ...$messages): void
     {
         try {
+            $messages = array_map(static function (Message $message) {
+                return $message->header(Header::EVENT_ID) === null
+                    ? $message->withHeader(Header::EVENT_ID, Uuid::uuid4()->toString())
+                    : $message;
+            }, $messages);
+
             $this->connection->beginTransaction();
 
             try {
diff --git a/src/DoctrineV2Outbox/DoctrineTransactionalMessageRepository.php b/src/DoctrineV2Outbox/DoctrineTransactionalMessageRepository.php
index 1987bcd..62592cf 100644
--- a/src/DoctrineV2Outbox/DoctrineTransactionalMessageRepository.php
+++ b/src/DoctrineV2Outbox/DoctrineTransactionalMessageRepository.php
@@ -4,12 +4,14 @@
 
 use Doctrine\DBAL\Connection;
 use EventSauce\EventSourcing\AggregateRootId;
+use EventSauce\EventSourcing\Header;
 use EventSauce\EventSourcing\Message;
 use EventSauce\EventSourcing\MessageRepository;
 use EventSauce\EventSourcing\PaginationCursor;
 use EventSauce\EventSourcing\UnableToPersistMessages;
 use EventSauce\MessageOutbox\OutboxRepository;
 use Generator;
+use Ramsey\Uuid\Uuid;
 use Throwable;
 
 class DoctrineTransactionalMessageRepository implements MessageRepository
@@ -23,6 +25,12 @@ public function __construct(
     public function persist(Message ...$messages): void
     {
         try {
+            $messages = array_map(static function (Message $message) {
+                return $message->header(Header::EVENT_ID) === null
+                    ? $message->withHeader(Header::EVENT_ID, Uuid::uuid4()->toString())
+                    : $message;
+            }, $messages);
+
             $this->connection->beginTransaction();
 
             try {
diff --git a/src/IlluminateOutbox/IlluminateTransactionalMessageRepository.php b/src/IlluminateOutbox/IlluminateTransactionalMessageRepository.php
index 1ae9740..554126d 100644
--- a/src/IlluminateOutbox/IlluminateTransactionalMessageRepository.php
+++ b/src/IlluminateOutbox/IlluminateTransactionalMessageRepository.php
@@ -3,6 +3,7 @@
 namespace EventSauce\MessageOutbox\IlluminateOutbox;
 
 use EventSauce\EventSourcing\AggregateRootId;
+use EventSauce\EventSourcing\Header;
 use EventSauce\EventSourcing\Message;
 use EventSauce\EventSourcing\MessageRepository;
 use EventSauce\EventSourcing\PaginationCursor;
@@ -10,6 +11,7 @@
 use EventSauce\MessageOutbox\OutboxRepository;
 use Generator;
 use Illuminate\Database\ConnectionInterface;
+use Ramsey\Uuid\Uuid;
 use Throwable;
 
 class IlluminateTransactionalMessageRepository implements MessageRepository
@@ -24,6 +26,12 @@ public function __construct(
     public function persist(Message ...$messages): void
     {
         try {
+            $messages = array_map(static function (Message $message) {
+                return $message->header(Header::EVENT_ID) === null
+                    ? $message->withHeader(Header::EVENT_ID, Uuid::uuid4()->toString())
+                    : $message;
+            }, $messages);
+
             $this->connection->beginTransaction();
 
             try {
diff --git a/src/TestTooling/TransactionalMessageRepositoryTestCase.php b/src/TestTooling/TransactionalMessageRepositoryTestCase.php
index db9a845..17ad7d6 100644
--- a/src/TestTooling/TransactionalMessageRepositoryTestCase.php
+++ b/src/TestTooling/TransactionalMessageRepositoryTestCase.php
@@ -107,6 +107,34 @@ public function messages_are_not_stored_in_the_outbox_when_the_repository_fails(
         self::assertEquals(0, $outboxRepository->numberOfMessages());
     }
 
+    /**
+     * @test
+     */
+    public function messages_are_persisted_with_consistent_ids(): void
+    {
+        $messageRepository = $this->messageRepository();
+        $outboxRepository = $this->outboxRepository();
+        $transactionalRepository = $this->transactionalRepository();
+        $message1 = $this->createMessageWithoutId('one', 1);
+        $message2 = $this->createMessageWithoutId('two', 2);
+        $message3 = $this->createMessageWithoutId('three', 3);
+        $message4 = $this->createMessageWithoutId('four', 4);
+
+        $transactionalRepository->persist($message1, $message2, $message3, $message4);
+
+        $messageIds = array_map(
+            static fn (Message $message) => $message->header(Header::EVENT_ID),
+            iterator_to_array($messageRepository->retrieveAll($this->aggregateRootId)),
+        );
+
+        $messageIdsInOutbox = array_map(
+            static fn (Message $message) => $message->header(Header::EVENT_ID),
+            iterator_to_array($outboxRepository->retrieveBatch(10)),
+        );
+
+        self::assertSame($messageIds, $messageIdsInOutbox);
+    }
+
     /**
      * @test
      */
@@ -137,4 +165,13 @@ protected function createMessage(string $value, int $version): Message
 
         return (new DefaultHeadersDecorator())->decorate($message);
     }
+
+    protected function createMessageWithoutId(string $value, int $version): Message
+    {
+        $message = (new Message(new DummyEvent($value)))
+            ->withHeader(Header::AGGREGATE_ROOT_ID, $this->aggregateRootId)
+            ->withHeader(Header::AGGREGATE_ROOT_VERSION, $version);
+
+        return (new DefaultHeadersDecorator())->decorate($message);
+    }
 }