diff --git a/lib/Doctrine/ORM/Query/SqlWalker.php b/lib/Doctrine/ORM/Query/SqlWalker.php
index 713f5534e..6e2e41ddc 100644
--- a/lib/Doctrine/ORM/Query/SqlWalker.php
+++ b/lib/Doctrine/ORM/Query/SqlWalker.php
@@ -888,7 +888,7 @@ class SqlWalker implements TreeWalker
      *
      * @return string
      */
-    private function generateRangeVariableDeclarationSQL($rangeVariableDeclaration, $buildNestedJoins)
+    private function generateRangeVariableDeclarationSQL($rangeVariableDeclaration, bool $buildNestedJoins) : string
     {
         $class    = $this->em->getClassMetadata($rangeVariableDeclaration->abstractSchemaName);
         $dqlAlias = $rangeVariableDeclaration->aliasIdentificationVariable;
diff --git a/tests/Doctrine/Tests/ORM/Functional/Ticket/GH6464Test.php b/tests/Doctrine/Tests/ORM/Functional/Ticket/GH6464Test.php
index adc6f7b16..1d75cdf3d 100644
--- a/tests/Doctrine/Tests/ORM/Functional/Ticket/GH6464Test.php
+++ b/tests/Doctrine/Tests/ORM/Functional/Ticket/GH6464Test.php
@@ -12,7 +12,7 @@ class GH6464Test extends OrmFunctionalTestCase
     /**
      * {@inheritDoc}
      */
-    protected function setUp()
+    protected function setUp() : void
     {
         parent::setUp();
 
@@ -29,7 +29,7 @@ class GH6464Test extends OrmFunctionalTestCase
      * SqlWalker needs to generate nested INNER JOIN statements, otherwise there would be INNER JOIN
      * statements without an ON clause, which are valid on e.g. MySQL but rejected by PostgreSQL.
      */
-    public function testIssue()
+    public function testIssue() : void
     {
         $query = $this->_em->createQueryBuilder()
             ->select('p')