diff --git a/src/PermissionRegistrar.php b/src/PermissionRegistrar.php
index ffb12d87e..bc434e571 100644
--- a/src/PermissionRegistrar.php
+++ b/src/PermissionRegistrar.php
@@ -142,7 +142,7 @@ public function forgetCachedPermissions()
         return $this->cache->forget($this->cacheKey);
     }
 
-    public function forgetWildcardPermissionIndex(?Model $record = null): void
+    public function forgetWildcardPermissionIndex(Model $record = null): void
     {
         if ($record) {
             unset($this->wildcardPermissionsIndex[get_class($record)][$record->getKey()]);