diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7c56eae..126e30d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,6 +17,8 @@ jobs:
         include:
           - php-versions: '7.1'
             cs-fixer: false
+          - php-versions: '8.1'
+            cs-fixer: false
     steps:
       - name: Checkout
         uses: actions/checkout@v2
diff --git a/Core/Frameworks/Flake/Core/Collection.php b/Core/Frameworks/Flake/Core/Collection.php
index 09ead65..0a5c490 100644
--- a/Core/Frameworks/Flake/Core/Collection.php
+++ b/Core/Frameworks/Flake/Core/Collection.php
@@ -39,15 +39,15 @@ class Collection extends \Flake\Core\FLObject implements \Iterator {
         return key($this->aCollection);
     }
 
-    function next() {
-        return next($this->aCollection);
+    function next(): void {
+        next($this->aCollection);
     }
 
-    function rewind() {
+    function rewind(): void {
         $this->reset();
     }
 
-    function valid() {
+    function valid(): bool {
         $key = key($this->aCollection);
 
         return ($key !== null && $key !== false);
diff --git a/Core/Frameworks/Flake/Core/Datastructure/Chain.php b/Core/Frameworks/Flake/Core/Datastructure/Chain.php
index 1f1b54b..28cee23 100644
--- a/Core/Frameworks/Flake/Core/Datastructure/Chain.php
+++ b/Core/Frameworks/Flake/Core/Datastructure/Chain.php
@@ -31,12 +31,12 @@ namespace Flake\Core\Datastructure;
  * @extends \SplDoublyLinkedList<\Flake\Core\Datastructure\Chainable>
  */
 class Chain extends \SplDoublyLinkedList {
-    function push($value) {
+    function push($value): void {
         $value->chain($this, $this->count());
         parent::push($value);
     }
 
-    function offsetUnset($offset) {
+    function offsetUnset($offset): void {
         throw new \Exception("Cannot delete Chainable in Chain");
     }
 
diff --git a/Core/Frameworks/Flake/Core/Datastructure/ChainLink.php b/Core/Frameworks/Flake/Core/Datastructure/ChainLink.php
index cc046d3..313569f 100644
--- a/Core/Frameworks/Flake/Core/Datastructure/ChainLink.php
+++ b/Core/Frameworks/Flake/Core/Datastructure/ChainLink.php
@@ -36,7 +36,7 @@ abstract class ChainLink implements \Flake\Core\Datastructure\Chainable {
         $this->__key = $key;
     }
 
-    function offsetSet($offset, $value) {
+    function offsetSet($offset, $value): void {
         if (is_null($this->__container)) {
             return;
         }
@@ -44,7 +44,7 @@ abstract class ChainLink implements \Flake\Core\Datastructure\Chainable {
         $this->__container->offsetSet($offset, $value);
     }
 
-    function offsetExists($offset) {
+    function offsetExists($offset): bool {
         if (is_null($this->__container)) {
             return false;
         }
@@ -52,7 +52,7 @@ abstract class ChainLink implements \Flake\Core\Datastructure\Chainable {
         return $this->__container->offsetExists($offset);
     }
 
-    function offsetUnset($offset) {
+    function offsetUnset($offset): void {
         if (is_null($this->__container)) {
             return;
         }
@@ -70,7 +70,7 @@ abstract class ChainLink implements \Flake\Core\Datastructure\Chainable {
         return $oRes;
     }
 
-    function rewind() {
+    function rewind(): void {
         $this->__container->rewind();
     }
 
@@ -82,10 +82,8 @@ abstract class ChainLink implements \Flake\Core\Datastructure\Chainable {
         return $this->__container->key();
     }
 
-    function &next() {
-        $oRes = $this->__container->next();
-
-        return $oRes;
+    function &next(): void {
+        $this->__container->next();
     }
 
     function &prev() {
@@ -94,11 +92,11 @@ abstract class ChainLink implements \Flake\Core\Datastructure\Chainable {
         return $oPrev;
     }
 
-    function valid() {
+    function valid(): bool {
         return $this->__container->valid();
     }
 
-    function count() {
+    function count(): int {
         return $this->__container->count();
     }