diff --git a/core/modules/rdf/rdf.module b/core/modules/rdf/rdf.module
index ca8d8ae..1dfde6a 100644
--- a/core/modules/rdf/rdf.module
+++ b/core/modules/rdf/rdf.module
@@ -498,10 +498,8 @@ function rdf_preprocess_comment(&$variables) {
   }
   // Adds RDF metadata markup above comment body.
   if (!empty($variables['rdf_metadata_attributes'])) {
-    if (!isset($variables['content']['comment_body']['#prefix'])) {
-      $prefix = '';
-    }
-    else {
+    $prefix = '';
+    if (!empty($variables['content']['comment_body']['#prefix'])) {
       $prefix = SafeMarkup::checkAdminXss($variables['content']['comment_body']['#prefix']);
     }
     $rdf_metadata = array(