diff --git a/src/Serializer/Normalizer/MoneyAsDecimalNormalizer.php b/src/Serializer/Normalizer/MoneyAsDecimalNormalizer.php
index b7fdd61..681d77b 100644
--- a/src/Serializer/Normalizer/MoneyAsDecimalNormalizer.php
+++ b/src/Serializer/Normalizer/MoneyAsDecimalNormalizer.php
@@ -2,7 +2,7 @@
 /*
  * This file is part of the Symfony HeadsnetMoneyBundle.
  *
- * (c) Headstrong Internet Services Ltd 2021
+ * (c) Headstrong Internet Services Ltd 2022
  *
  * For the full copyright and license information, please view the LICENSE
  * file that was distributed with this source code.
@@ -51,7 +51,7 @@ public function normalize($object, $format = null, array $context = [])
     /**
      * {@inheritdoc}
      */
-    public function supportsNormalization($data, $format = null)
+    public function supportsNormalization($data, $format = null): bool
     {
         return $data instanceof Money;
     }
diff --git a/src/Serializer/Normalizer/MoneyNormalizer.php b/src/Serializer/Normalizer/MoneyNormalizer.php
index 49e871a..8f606c1 100644
--- a/src/Serializer/Normalizer/MoneyNormalizer.php
+++ b/src/Serializer/Normalizer/MoneyNormalizer.php
@@ -2,7 +2,7 @@
 /*
  * This file is part of the Symfony HeadsnetMoneyBundle.
  *
- * (c) Headstrong Internet Services Ltd 2021
+ * (c) Headstrong Internet Services Ltd 2022
  *
  * For the full copyright and license information, please view the LICENSE
  * file that was distributed with this source code.
@@ -38,7 +38,7 @@ public function normalize($object, $format = null, array $context = [])
     /**
      * {@inheritdoc}
      */
-    public function supportsNormalization($data, $format = null)
+    public function supportsNormalization($data, $format = null): bool
     {
         return $data instanceof Money;
     }
@@ -59,7 +59,7 @@ public function denormalize($object, $class, $format = null, array $context = []
     /**
      * @inheritdoc
      */
-    public function supportsDenormalization($object, $type, $format = null)
+    public function supportsDenormalization($object, $type, $format = null): bool
     {
         if ($type !== Money::class) {
             return false;
diff --git a/src/Validator/Constraints/MoneyGreaterThan.php b/src/Validator/Constraints/MoneyGreaterThan.php
index b1da29e..0b234bb 100644
--- a/src/Validator/Constraints/MoneyGreaterThan.php
+++ b/src/Validator/Constraints/MoneyGreaterThan.php
@@ -2,7 +2,7 @@
 /*
  * This file is part of the Symfony HeadsnetMoneyBundle.
  *
- * (c) Headstrong Internet Services Ltd 2021
+ * (c) Headstrong Internet Services Ltd 2022
  *
  * For the full copyright and license information, please view the LICENSE
  * file that was distributed with this source code.
@@ -31,7 +31,7 @@ class MoneyGreaterThan extends Constraint
     /**
      * {@inheritdoc}
      */
-    public function getDefaultOption()
+    public function getDefaultOption(): ?string
     {
         return 'compareWith';
     }
diff --git a/src/Validator/Constraints/MoneyGreaterThanOrEqual.php b/src/Validator/Constraints/MoneyGreaterThanOrEqual.php
index 64ae5d7..20b9e81 100644
--- a/src/Validator/Constraints/MoneyGreaterThanOrEqual.php
+++ b/src/Validator/Constraints/MoneyGreaterThanOrEqual.php
@@ -2,7 +2,7 @@
 /*
  * This file is part of the Symfony HeadsnetMoneyBundle.
  *
- * (c) Headstrong Internet Services Ltd 2021
+ * (c) Headstrong Internet Services Ltd 2022
  *
  * For the full copyright and license information, please view the LICENSE
  * file that was distributed with this source code.
@@ -31,7 +31,7 @@ class MoneyGreaterThanOrEqual extends Constraint
     /**
      * {@inheritdoc}
      */
-    public function getDefaultOption()
+    public function getDefaultOption(): ?string
     {
         return 'compareWith';
     }