diff --git a/composer.json b/composer.json
index e5a377a..bbba406 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,7 @@
 	}
 	],
 	"require" : {
-		"php" : ">=7.0",
+		"php" : ">=7.1",
 		"doctrine/orm" : "~2.4",
 		"mouf/database.dao-interface" : "2.*",
 		"mouf/utils.common.doctrine-annotations-wrapper" : "~1.2",
diff --git a/src/EntityManager.php b/src/EntityManager.php
index ac9cbbd..9a78ac7 100644
--- a/src/EntityManager.php
+++ b/src/EntityManager.php
@@ -247,7 +247,7 @@ public function remove($entityName \$entity)
      *
      * @return $entityName|null
      */
-    public function findUniqueBy(array \$criteria)
+    public function findUniqueBy(array \$criteria) : ?$entityName
     {
         \$result = \$this->findBy(\$criteria);