diff --git a/lib/Controller/PageController.php b/lib/Controller/PageController.php
index 735b4369..b5846e12 100644
--- a/lib/Controller/PageController.php
+++ b/lib/Controller/PageController.php
@@ -180,7 +180,7 @@ function setEmbCsp($tr, $userId) {
             $csp = new ContentSecurityPolicy();
             $tr->setContentSecurityPolicy($csp);
         }
-        $csp->addAllowedFrameAncestorDomain("'*'");
+        $csp->addAllowedFrameAncestorDomain("*");
     }
 
     // ---- END EMBEDDABLE -----