diff --git a/Helper/MarkdownHelper.php b/Helper/MarkdownHelper.php
index 0b3974f..fc7de2d 100644
--- a/Helper/MarkdownHelper.php
+++ b/Helper/MarkdownHelper.php
@@ -50,7 +50,7 @@ class MarkdownHelper implements HelperInterface
      *
      * @return string The default charset
      */
-    public function getCharset()
+    public function getCharset(): string
     {
         return $this->charset;
     }
diff --git a/Parser/Preset/Light.php b/Parser/Preset/Light.php
index aac1b95..ca12e7c 100644
--- a/Parser/Preset/Light.php
+++ b/Parser/Preset/Light.php
@@ -12,7 +12,7 @@ class Light extends MarkdownParser
     /**
      * @var array Enabled features
      */
-    protected $features = array(
+    protected array $features = array(
         'header' => true,
         'list' => true,
         'horizontal_rule' => true,
diff --git a/Parser/Preset/Medium.php b/Parser/Preset/Medium.php
index 3de4d1e..70ddd89 100644
--- a/Parser/Preset/Medium.php
+++ b/Parser/Preset/Medium.php
@@ -12,7 +12,7 @@ class Medium extends MarkdownParser
     /**
      * @var array Enabled features
      */
-    protected $features = array(
+    protected array $features = array(
         'header' => true,
         'list' => true,
         'horizontal_rule' => true,
diff --git a/tests/IntegrationTest.php b/tests/IntegrationTest.php
index 7c88445..d86dee4 100644
--- a/tests/IntegrationTest.php
+++ b/tests/IntegrationTest.php
@@ -31,7 +31,7 @@ class IntegrationKernel extends Kernel
 
     private $cacheDir;
 
-    public function registerBundles()
+    public function registerBundles(): iterable
     {
         return [
             new FrameworkBundle(),
@@ -52,7 +52,7 @@ class IntegrationKernel extends Kernel
             ]);
     }
 
-    public function getCacheDir()
+    public function getCacheDir(): string
     {
         if (null === $this->cacheDir) {
             $this->cacheDir = sys_get_temp_dir().'/'.rand(100, 999);
diff --git a/tests/fixtures/app/TestKernel.php b/tests/fixtures/app/TestKernel.php
index b5cb93d..26cf034 100644
--- a/tests/fixtures/app/TestKernel.php
+++ b/tests/fixtures/app/TestKernel.php
@@ -12,7 +12,7 @@ use Symfony\Component\HttpKernel\Kernel;
 
 class TestKernel extends Kernel
 {
-    public function registerBundles()
+    public function registerBundles(): iterable
     {
         return array(
             new FrameworkBundle(),
@@ -31,4 +31,4 @@ class TestKernel extends Kernel
             $c->setAlias('markdown.parser.parser_manager.public', new Alias('markdown.parser.parser_manager', true));
         });
     }
-}
\ No newline at end of file
+}