diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 316c572..777738d 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -11,7 +11,7 @@ jobs:
         strategy:
             fail-fast: false
             matrix:
-                php: [8.1, 8.2, 8.3]
+                php: [8.1, 8.2, 8.3, 8.4]
                 dependency-version: [prefer-stable]
                 os: [ubuntu-latest]
 
@@ -19,7 +19,7 @@ jobs:
 
         steps:
             - name: Checkout code
-              uses: actions/checkout@v2
+              uses: actions/checkout@v4
 
             - name: Setup PHP
               uses: shivammathur/setup-php@v2
@@ -42,7 +42,7 @@ jobs:
 
         steps:
             - name: Checkout code
-              uses: actions/checkout@v2
+              uses: actions/checkout@v4
               with:
                   fetch-depth: 0
 
@@ -71,7 +71,7 @@ jobs:
 
         steps:
             - name: Checkout code
-              uses: actions/checkout@v2
+              uses: actions/checkout@v4
 
             - name: Setup PHP
               uses: shivammathur/setup-php@v2
diff --git a/src/CasesCollection.php b/src/CasesCollection.php
index 6d8e17c..c74686c 100644
--- a/src/CasesCollection.php
+++ b/src/CasesCollection.php
@@ -115,7 +115,7 @@ public function toArray(): array
      * @param (callable(TValue, array-key): bool)|null $callback
      * @return ?TValue
      */
-    public function first(callable $callback = null): mixed
+    public function first(callable|null $callback = null): mixed
     {
         $callback ??= fn() => true;
 
@@ -159,7 +159,7 @@ public function values(): array
      * @param (callable(TValue): array-key)|string|null $key
      * @return array<array-key, TPluckValue>
      */
-    public function pluck(callable|string $value, callable|string $key = null): array
+    public function pluck(callable|string $value, callable|string|null $key = null): array
     {
         $result = [];
 
diff --git a/src/Concerns/CollectsCases.php b/src/Concerns/CollectsCases.php
index 2be87dd..8e1e9aa 100644
--- a/src/Concerns/CollectsCases.php
+++ b/src/Concerns/CollectsCases.php
@@ -32,7 +32,7 @@ public static function count(): int
      *
      * @param (callable(self, array-key): bool)|null $callback
      */
-    public static function first(callable $callback = null): ?self
+    public static function first(callable|null $callback = null): ?self
     {
         return self::collect()->first($callback);
     }
@@ -66,7 +66,7 @@ public static function values(): array
      * @param (callable(self): array-key)|string|null $key
      * @return array<array-key, TPluckValue>
      */
-    public static function pluck(callable|string $value, callable|string $key = null): array
+    public static function pluck(callable|string $value, callable|string|null $key = null): array
     {
         return self::collect()->pluck($value, $key);
     }