diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index b60478ab..676ea7c3 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -19,6 +19,7 @@ jobs:
           - "7.3"
           - "7.4"
           - "8.0"
+          - "8.1"
         dependencies:
           - "lowest"
           - "highest"
@@ -45,9 +46,11 @@ jobs:
             symfony-yaml: '^6'
           - php: '7.4'
             symfony-yaml: '^6'
-          # symfony/yaml v3.4 is not compatible with PHP 8.0 but has no upper-bound, so it installs on it
+          # symfony/yaml v3.4 is not compatible with PHP 8.0+ but has no upper-bound, so it installs on it
           - php: '8.0'
             symfony-yaml: '^3.4'
+          - php: '8.1'
+            symfony-yaml: '^3.4'
 
     runs-on: ${{ matrix.os }}
 
diff --git a/composer.json b/composer.json
index 46cb26f2..6b9bae5b 100644
--- a/composer.json
+++ b/composer.json
@@ -25,7 +25,7 @@
 	},
 	"require-dev": {
 		"cebe/indent": "*",
-		"phpunit/phpunit": "^6.5 || ^7.5 || ^8.5 || ^9.4",
+		"phpunit/phpunit": "^6.5 || ^7.5 || ^8.5.14 || ^9.4",
 		"oai/openapi-specification": "3.0.3",
 		"mermade/openapi3-examples": "1.0.0",
 		"apis-guru/openapi-directory": "1.0.0",
diff --git a/src/json/JsonReference.php b/src/json/JsonReference.php
index fe27ced1..cfac559e 100644
--- a/src/json/JsonReference.php
+++ b/src/json/JsonReference.php
@@ -126,6 +126,7 @@ public function getReference(): string
      * @return mixed data which can be serialized by <b>json_encode</b>,
      * which is a value of any type other than a resource.
      */
+    #[\ReturnTypeWillChange]
     public function jsonSerialize()
     {
         return (object)['$ref' => $this->getReference()];
diff --git a/src/spec/Paths.php b/src/spec/Paths.php
index a2da8a10..f1ebdc2f 100644
--- a/src/spec/Paths.php
+++ b/src/spec/Paths.php
@@ -183,6 +183,7 @@ public function getErrors(): array
      * @return boolean true on success or false on failure.
      * The return value will be casted to boolean if non-boolean was returned.
      */
+    #[\ReturnTypeWillChange]
     public function offsetExists($offset)
     {
         return $this->hasPath($offset);
@@ -194,6 +195,7 @@ public function offsetExists($offset)
      * @param mixed $offset The offset to retrieve.
      * @return PathItem Can return all value types.
      */
+    #[\ReturnTypeWillChange]
     public function offsetGet($offset)
     {
         return $this->getPath($offset);
@@ -205,6 +207,7 @@ public function offsetGet($offset)
      * @param mixed $offset The offset to assign the value to.
      * @param mixed $value The value to set.
      */
+    #[\ReturnTypeWillChange]
     public function offsetSet($offset, $value)
     {
         $this->addPath($offset, $value);
@@ -215,6 +218,7 @@ public function offsetSet($offset, $value)
      * @link http://php.net/manual/en/arrayaccess.offsetunset.php
      * @param mixed $offset The offset to unset.
      */
+    #[\ReturnTypeWillChange]
     public function offsetUnset($offset)
     {
         $this->removePath($offset);
@@ -226,6 +230,7 @@ public function offsetUnset($offset)
      * @return int The custom count as an integer.
      * The return value is cast to an integer.
      */
+    #[\ReturnTypeWillChange]
     public function count()
     {
         return count($this->_paths);
@@ -236,6 +241,7 @@ public function count()
      * @link http://php.net/manual/en/iteratoraggregate.getiterator.php
      * @return Traversable An instance of an object implementing <b>Iterator</b> or <b>Traversable</b>
      */
+    #[\ReturnTypeWillChange]
     public function getIterator()
     {
         return new ArrayIterator($this->_paths);
diff --git a/src/spec/Responses.php b/src/spec/Responses.php
index 52476031..d2d5d855 100644
--- a/src/spec/Responses.php
+++ b/src/spec/Responses.php
@@ -173,6 +173,7 @@ public function getErrors(): array
      * @return boolean true on success or false on failure.
      * The return value will be casted to boolean if non-boolean was returned.
      */
+    #[\ReturnTypeWillChange]
     public function offsetExists($offset)
     {
         return $this->hasResponse($offset);
@@ -184,6 +185,7 @@ public function offsetExists($offset)
      * @param mixed $offset The offset to retrieve.
      * @return mixed Can return all value types.
      */
+    #[\ReturnTypeWillChange]
     public function offsetGet($offset)
     {
         return $this->getResponse($offset);
@@ -195,6 +197,7 @@ public function offsetGet($offset)
      * @param mixed $offset The offset to assign the value to.
      * @param mixed $value The value to set.
      */
+    #[\ReturnTypeWillChange]
     public function offsetSet($offset, $value)
     {
         $this->addResponse($offset, $value);
@@ -205,6 +208,7 @@ public function offsetSet($offset, $value)
      * @link http://php.net/manual/en/arrayaccess.offsetunset.php
      * @param mixed $offset The offset to unset.
      */
+    #[\ReturnTypeWillChange]
     public function offsetUnset($offset)
     {
         $this->removeResponse($offset);
@@ -216,6 +220,7 @@ public function offsetUnset($offset)
      * @return int The custom count as an integer.
      * The return value is cast to an integer.
      */
+    #[\ReturnTypeWillChange]
     public function count()
     {
         return count($this->_responses);
@@ -226,6 +231,7 @@ public function count()
      * @link http://php.net/manual/en/iteratoraggregate.getiterator.php
      * @return Traversable An instance of an object implementing <b>Iterator</b> or <b>Traversable</b>
      */
+    #[\ReturnTypeWillChange]
     public function getIterator()
     {
         return new ArrayIterator($this->_responses);