 @@ -57,4 +57,4 @@ interface DenormalizerInterface
       * @return bool
       */
--    public function supportsDenormalization(mixed $data, string $type, string $format = null /*, array $context = [] */);
-+    public function supportsDenormalization(mixed $data, string $type, string $format = null /*, array $context = [] */): bool;
+-    public function supportsDenormalization(mixed $data, string $type, string $format = null /* , array $context = [] */);
++    public function supportsDenormalization(mixed $data, string $type, string $format = null /* , array $context = [] */): bool;
  }
 diff --git a/src/Symfony/Component/Serializer/Normalizer/NormalizerInterface.php b/src/Symfony/Component/Serializer/Normalizer/NormalizerInterface.php
 index 741f19e50b..acf3be931b 100644

@@ -45,4 +45,4 @@ interface DecoderInterface
      * @return bool
      */
-    public function supportsDecoding(string $format /*, array $context = [] */);
+    public function supportsDecoding(string $format /*, array $context = [] */): bool;
 }
diff --git a/src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php b/src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php
index 44ba45f581..3398115497 100644

@@ -139,5 +139,5 @@ abstract class AbstractObjectNormalizer extends AbstractNormalizer
      * @param array $context
      */
-    public function supportsNormalization(mixed $data, string $format = null /* , array $context = [] */)
+    public function supportsNormalization(mixed $data, string $format = null /* , array $context = [] */): bool
     {
         return \is_object($data) && !$data instanceof \Traversable;
@@ -147,5 +147,5 @@ abstract class AbstractObjectNormalizer extends AbstractNormalizer
