diff --git a/tests/TestClasses/FakeCacheCheck.php b/tests/TestClasses/FakeCacheCheck.php
index 082141ad..50baa1a5 100644
--- a/tests/TestClasses/FakeCacheCheck.php
+++ b/tests/TestClasses/FakeCacheCheck.php
@@ -16,7 +16,7 @@ public function replyWith(Closure $closure): self
         return $this;
     }
 
-    public function canWriteValuesToCache(string $driver): bool
+    public function canWriteValuesToCache(?string $driver): bool
     {
         return ($this->closure)();
     }