diff --git a/Plugin/AddCspInlineScripts.php b/Plugin/AddCspInlineScripts.php
index 528a843..bf818c4 100644
--- a/Plugin/AddCspInlineScripts.php
+++ b/Plugin/AddCspInlineScripts.php
@@ -26,7 +26,7 @@ public function afterToHtml(Template $block, $html): string
         }
 
         if (false === strstr((string)$block->getNameInLayout(), 'yireo_googletagmanager2.')) {
-            return $html;
+            return (string)$html;
         }
 
         $scripts = $this->scriptFinder->find($html);