diff --git a/.github/workflows/run-static-analysis.yml b/.github/workflows/run-static-analysis.yml
index b2f6796..692c29f 100644
--- a/.github/workflows/run-static-analysis.yml
+++ b/.github/workflows/run-static-analysis.yml
@@ -22,7 +22,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: [8.1, 8.2, 8.3]
+        php: [8.1, 8.2, 8.3, 8.4]
         laravel: [9.*, 10.*, 11.*]
         dependency-version: [prefer-stable]
         exclude:
diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
index f9818bb..75dc13a 100644
--- a/.github/workflows/run-tests.yml
+++ b/.github/workflows/run-tests.yml
@@ -22,7 +22,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: [8.1, 8.2, 8.3]
+        php: [8.1, 8.2, 8.3, 8.4]
         laravel: ['9.*', '10.*', '11.*']
         dependency-version: [prefer-lowest, prefer-stable]
         exclude:
diff --git a/src/PDF.php b/src/PDF.php
index c2c8027..10d7918 100644
--- a/src/PDF.php
+++ b/src/PDF.php
@@ -193,7 +193,7 @@ public function output(array $options = []): string
     /**
      * Save the PDF to a file
      */
-    public function save(string $filename, string $disk = null): self
+    public function save(string $filename, ?string $disk = null): self
     {
         $disk = $disk ?: $this->config->get('dompdf.disk');