diff --git a/composer.json b/composer.json
index d3a2b7f..d96a806 100644
--- a/composer.json
+++ b/composer.json
@@ -4,7 +4,7 @@
   "license": "MIT",
   "require": {
     "php": ">=7.2",
-    "broadway/broadway-saga": "~0.8",
+    "broadway/broadway-saga": "~0.10",
     "doctrine/mongodb": "^1.0",
     "beberlei/assert": "^3.0",
     "alcaeus/mongo-php-adapter": "^1.1"
diff --git a/src/MongoDBRepository.php b/src/MongoDBRepository.php
index 9f97145..960dba1 100644
--- a/src/MongoDBRepository.php
+++ b/src/MongoDBRepository.php
@@ -31,7 +31,7 @@ public function __construct(Collection $collection)
     /**
      * {@inheritdoc}
      */
-    public function findOneBy(Criteria $criteria, $sagaId)
+    public function findOneBy(Criteria $criteria, $sagaId): ?State
     {
         $query = $this->createQuery($criteria, $sagaId);
         $results = $query->execute();
@@ -51,7 +51,7 @@ public function findOneBy(Criteria $criteria, $sagaId)
     /**
      * {@inheritdoc}
      */
-    public function save(State $state, $sagaId)
+    public function save(State $state, $sagaId): void
     {
         $serializedState = $state->serialize();
         $serializedState['_id'] = $serializedState['id'];
diff --git a/test/MongoDBRepositoryTest.php b/test/MongoDBRepositoryTest.php
index e3dadb6..3697b6f 100644
--- a/test/MongoDBRepositoryTest.php
+++ b/test/MongoDBRepositoryTest.php
@@ -13,6 +13,7 @@
 
 namespace Broadway\Saga\State\MongoDB;
 
+use Broadway\Saga\State\RepositoryInterface;
 use Broadway\Saga\State\Testing\AbstractRepositoryTest;
 use Doctrine\MongoDB\Configuration;
 use Doctrine\MongoDB\Connection;
@@ -22,7 +23,7 @@ class MongoDBRepositoryTest extends AbstractRepositoryTest
     protected static $dbName = 'doctrine_mongodb';
     protected $connection;
 
-    protected function createRepository()
+    protected function createRepository(): RepositoryInterface
     {
         $config = new Configuration();
         $config->setLoggerCallable(function ($msg) {});