diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 3b2e8d2..a30f70c 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -16,7 +16,7 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        php: [7.2, 7.3, 7.4, '8.0', 8.1, 8.2, 8.3]
+        php: [7.2, 7.3, 7.4, '8.0', 8.1, 8.2, 8.3, 8.4]
 
     name: PHP ${{ matrix.php }}
 
diff --git a/src/helpers.php b/src/helpers.php
index 54723ed..21e3342 100644
--- a/src/helpers.php
+++ b/src/helpers.php
@@ -81,7 +81,7 @@ function array_except($array, $keys)
      * @param  mixed  $default
      * @return mixed
      */
-    function array_first($array, callable $callback = null, $default = null)
+    function array_first($array, ?callable $callback = null, $default = null)
     {
         return Arr::first($array, $callback, $default);
     }
@@ -153,7 +153,7 @@ function array_has($array, $keys)
      * @param  mixed  $default
      * @return mixed
      */
-    function array_last($array, callable $callback = null, $default = null)
+    function array_last($array, ?callable $callback = null, $default = null)
     {
         return Arr::last($array, $callback, $default);
     }