diff --git a/src/bundle/Form/ChoiceLoader/ConfiguredLanguagesChoiceLoader.php b/src/bundle/Form/ChoiceLoader/ConfiguredLanguagesChoiceLoader.php
index 4894742..77e5712 100644
--- a/src/bundle/Form/ChoiceLoader/ConfiguredLanguagesChoiceLoader.php
+++ b/src/bundle/Form/ChoiceLoader/ConfiguredLanguagesChoiceLoader.php
@@ -42,7 +42,7 @@ public function getChoiceList(): array
     /**
      * {@inheritdoc}
      */
-    public function loadChoiceList(callable $value = null)
+    public function loadChoiceList(?callable $value = null)
     {
         $choices = $this->getChoiceList();
 
@@ -52,7 +52,7 @@ public function loadChoiceList(callable $value = null)
     /**
      * {@inheritdoc}
      */
-    public function loadChoicesForValues(array $values, callable $value = null)
+    public function loadChoicesForValues(array $values, ?callable $value = null)
     {
         // Optimize
         $values = array_filter($values);
@@ -66,7 +66,7 @@ public function loadChoicesForValues(array $values, callable $value = null)
     /**
      * {@inheritdoc}
      */
-    public function loadValuesForChoices(array $choices, callable $value = null)
+    public function loadValuesForChoices(array $choices, ?callable $value = null)
     {
         // Optimize
         $choices = array_filter($choices);
diff --git a/src/bundle/Form/ChoiceLoader/ContentTypeChoiceLoader.php b/src/bundle/Form/ChoiceLoader/ContentTypeChoiceLoader.php
index 4e1a1ed..39ec776 100644
--- a/src/bundle/Form/ChoiceLoader/ContentTypeChoiceLoader.php
+++ b/src/bundle/Form/ChoiceLoader/ContentTypeChoiceLoader.php
@@ -55,7 +55,7 @@ public function getChoiceList(): array
     /**
      * {@inheritdoc}
      */
-    public function loadChoiceList(callable $value = null)
+    public function loadChoiceList(?callable $value = null)
     {
         $choices = $this->getChoiceList();
 
@@ -65,7 +65,7 @@ public function loadChoiceList(callable $value = null)
     /**
      * {@inheritdoc}
      */
-    public function loadChoicesForValues(array $values, callable $value = null)
+    public function loadChoicesForValues(array $values, ?callable $value = null)
     {
         // Optimize
         $values = array_filter($values);
@@ -79,7 +79,7 @@ public function loadChoicesForValues(array $values, callable $value = null)
     /**
      * {@inheritdoc}
      */
-    public function loadValuesForChoices(array $choices, callable $value = null)
+    public function loadValuesForChoices(array $choices, ?callable $value = null)
     {
         // Optimize
         $choices = array_filter($choices);
diff --git a/src/contracts/Model/Suggestion/Suggestion.php b/src/contracts/Model/Suggestion/Suggestion.php
index cd88f3d..1298aa5 100644
--- a/src/contracts/Model/Suggestion/Suggestion.php
+++ b/src/contracts/Model/Suggestion/Suggestion.php
@@ -18,7 +18,7 @@ abstract class Suggestion extends ValueObject
 
     public function __construct(
         float $score,
-        string $name = null
+        ?string $name = null
     ) {
         $this->score = $score;
         $this->name = $name;
diff --git a/src/lib/Serializer/Normalizer/Suggestion/ContentSuggestionNormalizer.php b/src/lib/Serializer/Normalizer/Suggestion/ContentSuggestionNormalizer.php
index cba0d07..ed84c8d 100644
--- a/src/lib/Serializer/Normalizer/Suggestion/ContentSuggestionNormalizer.php
+++ b/src/lib/Serializer/Normalizer/Suggestion/ContentSuggestionNormalizer.php
@@ -26,7 +26,7 @@ final class ContentSuggestionNormalizer implements
      *
      * @return array<string, mixed>
      */
-    public function normalize($object, string $format = null, array $context = []): array
+    public function normalize($object, ?string $format = null, array $context = []): array
     {
         $content = $object->getContent();
 
@@ -41,7 +41,7 @@ public function normalize($object, string $format = null, array $context = []):
         ];
     }
 
-    public function supportsNormalization($data, string $format = null): bool
+    public function supportsNormalization($data, ?string $format = null): bool
     {
         return $data instanceof ContentSuggestion;
     }
diff --git a/src/lib/Serializer/Normalizer/Suggestion/LocationNormalizer.php b/src/lib/Serializer/Normalizer/Suggestion/LocationNormalizer.php
index f30960f..6b09a7c 100644
--- a/src/lib/Serializer/Normalizer/Suggestion/LocationNormalizer.php
+++ b/src/lib/Serializer/Normalizer/Suggestion/LocationNormalizer.php
@@ -18,7 +18,7 @@ final class LocationNormalizer implements NormalizerInterface
      *
      * @return array<string, mixed>
      */
-    public function normalize($object, string $format = null, array $context = []): array
+    public function normalize($object, ?string $format = null, array $context = []): array
     {
         return [
             'id' => $object->getContentInfo()->getId(),
@@ -27,7 +27,7 @@ public function normalize($object, string $format = null, array $context = []):
         ];
     }
 
-    public function supportsNormalization($data, string $format = null): bool
+    public function supportsNormalization($data, ?string $format = null): bool
     {
         return $data instanceof Location;
     }
diff --git a/src/lib/Serializer/Normalizer/Suggestion/ParentLocationCollectionNormalizer.php b/src/lib/Serializer/Normalizer/Suggestion/ParentLocationCollectionNormalizer.php
index 8e2a975..a0bb9fb 100644
--- a/src/lib/Serializer/Normalizer/Suggestion/ParentLocationCollectionNormalizer.php
+++ b/src/lib/Serializer/Normalizer/Suggestion/ParentLocationCollectionNormalizer.php
@@ -27,7 +27,7 @@ final class ParentLocationCollectionNormalizer implements
      *
      * @return array<int,mixed>.
      */
-    public function normalize($object, string $format = null, array $context = []): array
+    public function normalize($object, ?string $format = null, array $context = []): array
     {
         $normalizedData = [];
 
@@ -38,7 +38,7 @@ public function normalize($object, string $format = null, array $context = []):
         return $normalizedData;
     }
 
-    public function supportsNormalization($data, string $format = null): bool
+    public function supportsNormalization($data, ?string $format = null): bool
     {
         return $data instanceof ParentLocationCollection;
     }
diff --git a/src/lib/Serializer/Normalizer/Suggestion/SuggestionCollectionNormalizer.php b/src/lib/Serializer/Normalizer/Suggestion/SuggestionCollectionNormalizer.php
index 55a28b2..6908dc5 100644
--- a/src/lib/Serializer/Normalizer/Suggestion/SuggestionCollectionNormalizer.php
+++ b/src/lib/Serializer/Normalizer/Suggestion/SuggestionCollectionNormalizer.php
@@ -27,7 +27,7 @@ final class SuggestionCollectionNormalizer implements
      *
      * @return array<string,mixed>.
      */
-    public function normalize($object, string $format = null, array $context = []): array
+    public function normalize($object, ?string $format = null, array $context = []): array
     {
         $suggestionCollection = [];
 
@@ -41,7 +41,7 @@ public function normalize($object, string $format = null, array $context = []):
         ];
     }
 
-    public function supportsNormalization($data, string $format = null): bool
+    public function supportsNormalization($data, ?string $format = null): bool
     {
         return $data instanceof SuggestionCollection;
     }