diff --git a/.github/workflows/functionaltests.yml b/.github/workflows/functionaltests.yml
index 9937562..860019c 100644
--- a/.github/workflows/functionaltests.yml
+++ b/.github/workflows/functionaltests.yml
@@ -10,7 +10,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-version: [ 8.1, 8.2 ]
+        php-version: [ 8.1, 8.2, 8.3 ]
         flow-version: [ 8.3 ]
         mysql-version: [5.7]
 
diff --git a/.github/workflows/unittests.yml b/.github/workflows/unittests.yml
index ff99b5d..45daa51 100644
--- a/.github/workflows/unittests.yml
+++ b/.github/workflows/unittests.yml
@@ -10,7 +10,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-version: [ 8.1, 8.2 ]
+        php-version: [ 8.1, 8.2, 8.3 ]
         flow-version: [ 8.3 ]
 
     env:
diff --git a/Classes/Domain/Model/ResourceProxy.php b/Classes/Domain/Model/ResourceProxy.php
index e920d7f..b04e727 100644
--- a/Classes/Domain/Model/ResourceProxy.php
+++ b/Classes/Domain/Model/ResourceProxy.php
@@ -48,37 +48,37 @@ public function setPayload($payload = [])
     /**
      * @inheritdoc
      */
-    public function offsetExists($propertyName)
+    public function offsetExists(mixed $offset): bool
     {
-        return $this->type->getPropertyDefinition($propertyName) !== Type::PROPERTY_UNDEFINED;
+        return $this->type->getPropertyDefinition($offset) !== Type::PROPERTY_UNDEFINED;
     }
 
     /**
      * @inheritdoc
      */
-    public function offsetGet($propertyName)
+    public function offsetGet(mixed $offset): mixed
     {
-        switch ($this->type->getPropertyDefinition($propertyName)) {
+        switch ($this->type->getPropertyDefinition($offset)) {
             case Type::PROPERTY_ATTRIBUTE:
-                return $this->getAttribute($propertyName);
+                return $this->getAttribute($offset);
             case Type::PROPERTY_SINGLE_RELATIONSHIP:
-                return $this->getSingleRelationship($propertyName);
+                return $this->getSingleRelationship($offset);
             case Type::PROPERTY_COLLECTION_RELATIONSHIP:
-                return $this->getCollectionRelationship($propertyName);
+                return $this->getCollectionRelationship($offset);
         }
     }
 
     /**
      * @inheritdoc
      */
-    public function offsetSet($propertyName, $value)
+    public function offsetSet(mixed $offset, mixed $value): void
     {
     }
 
     /**
      * @inheritdoc
      */
-    public function offsetUnset($propertyName)
+    public function offsetUnset(mixed $offset): void
     {
     }
 
diff --git a/Classes/Domain/Model/ResourceProxyIterator.php b/Classes/Domain/Model/ResourceProxyIterator.php
index 0ee3a25..fdd8ebf 100644
--- a/Classes/Domain/Model/ResourceProxyIterator.php
+++ b/Classes/Domain/Model/ResourceProxyIterator.php
@@ -3,6 +3,7 @@
 
 namespace Netlogix\JsonApiOrg\Consumer\Domain\Model;
 
+use Generator;
 use Neos\Cache\Frontend\VariableFrontend;
 use Neos\Flow\Cache\CacheManager;
 use Neos\Flow\Utility\Now;
@@ -85,9 +86,9 @@ public function withJsonResult(array $jsonResult): self
     }
 
     /**
-     * @return \Generator
+     * @return Generator
      */
-    public function getIterator()
+    public function getIterator(): Generator
     {
         yield from $this->data;
     }
@@ -100,7 +101,7 @@ public function getArrayCopy(): array
     /**
      * @return int
      */
-    public function count()
+    public function count(): int
     {
         if (isset($this->jsonResult)
             && array_key_exists('meta', $this->jsonResult)