diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 5a786b1..30df493 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -18,7 +18,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Set up PHP ${{ matrix.php }}
         uses: shivammathur/setup-php@v2
diff --git a/src/Headers.php b/src/Headers.php
index c024886..038e792 100644
--- a/src/Headers.php
+++ b/src/Headers.php
@@ -178,7 +178,7 @@ protected function parseAuthorizationHeader(array $headers): array
     {
         $hasAuthorizationHeader = false;
         foreach ($headers as $name => $value) {
-            if (strtolower($name) === 'authorization') {
+            if (strtolower((string) $name) === 'authorization') {
                 $hasAuthorizationHeader = true;
                 break;
             }