diff --git a/src/Configuration/Metadata/Driver/AnnotationOrAttributeDriver.php b/src/Configuration/Metadata/Driver/AnnotationOrAttributeDriver.php
index 6b25852..dde9a7d 100644
--- a/src/Configuration/Metadata/Driver/AnnotationOrAttributeDriver.php
+++ b/src/Configuration/Metadata/Driver/AnnotationOrAttributeDriver.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Hateoas\Configuration\Metadata\Driver;
 
 use Hateoas\Configuration\Annotation;
diff --git a/src/Configuration/Metadata/Driver/AttributeDriver.php b/src/Configuration/Metadata/Driver/AttributeDriver.php
index d4258ac..b06ef83 100644
--- a/src/Configuration/Metadata/Driver/AttributeDriver.php
+++ b/src/Configuration/Metadata/Driver/AttributeDriver.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Hateoas\Configuration\Metadata\Driver;
 
 class AttributeDriver extends AnnotationOrAttributeDriver