diff --git a/tests/ContentTypeTest.php b/tests/ContentTypeTest.php
index 2c306f1..c4c407e 100644
--- a/tests/ContentTypeTest.php
+++ b/tests/ContentTypeTest.php
@@ -124,7 +124,7 @@ function ($request) {
         $this->assertFalse($response->hasHeader('X-Content-Type-Options'));
     }
 
-    public function charsetProvider(): array
+    public static function charsetProvider(): array
     {
         return [
             [