diff --git a/includes/callback_attachments_settings.inc b/includes/callback_attachments_settings.inc
index 37f95a8..ab16c69 100755
--- a/includes/callback_attachments_settings.inc
+++ b/includes/callback_attachments_settings.inc
@@ -427,7 +427,7 @@ class SearchApiAttachmentsAlterSettings extends SearchApiAbstractAlterCallback {
     if (in_array($scheme, array_keys($local_wrappers))) {
       return $wrapper->realpath();
     }
-    else {
+    elseif (is_object($wrapper)) {
       return $wrapper->getExternalUrl();
     }
   }