diff --git a/src/ServiceWorkerRule/ServiceWorkerRule.php b/src/ServiceWorkerRule/ServiceWorkerRule.php
index 64f0a83..88c0078 100644
--- a/src/ServiceWorkerRule/ServiceWorkerRule.php
+++ b/src/ServiceWorkerRule/ServiceWorkerRule.php
@@ -6,5 +6,5 @@
 
 interface ServiceWorkerRule
 {
-    public function process(): string;
+    public function process(bool $debug = false): string;
 }
diff --git a/src/ServiceWorkerRule/WindowsWidgets.php b/src/ServiceWorkerRule/WindowsWidgets.php
index d9a6245..bd90eb2 100644
--- a/src/ServiceWorkerRule/WindowsWidgets.php
+++ b/src/ServiceWorkerRule/WindowsWidgets.php
@@ -34,8 +34,9 @@ public function process(bool $debug = false): string
             return '';
         }
         $data = $this->serializer->serialize($tags, 'json', $this->serializerOptions($debug));
+        $declaration = '';
         if ($debug === true) {
-            $declaration = <<<DEBUG_COMMENT
+            $declaration .= <<<DEBUG_COMMENT
 
 
 /**************************************************** END WINDOWS WIDGETS ****************************************************/