diff --git a/src/Plugin/Field/FieldFormatter/IframeDefaultFormatter.php b/src/Plugin/Field/FieldFormatter/IframeDefaultFormatter.php
index b9ce461..3b11a44 100644
--- a/src/Plugin/Field/FieldFormatter/IframeDefaultFormatter.php
+++ b/src/Plugin/Field/FieldFormatter/IframeDefaultFormatter.php
@@ -135,6 +135,9 @@ class IframeDefaultFormatter extends FormatterBase {
     if (!empty($item->transparency) && $item->transparency > 0) {
         $options['transparency'] = (int)$item->transparency;
     }
+    else {
+        $options['frameborder'] = 0;
+    }
 
     $htmlid = '';
     if (isset($item->htmlid) && !empty($item->htmlid)) {