diff --git a/library/Icinga/Web/Form/Validator/InternalUrlValidator.php b/library/Icinga/Web/Form/Validator/InternalUrlValidator.php
index 07726824a..424e77ff8 100644
--- a/library/Icinga/Web/Form/Validator/InternalUrlValidator.php
+++ b/library/Icinga/Web/Form/Validator/InternalUrlValidator.php
@@ -16,7 +16,7 @@ class InternalUrlValidator extends Zend_Validate_Abstract
      */
     public function isValid($value)
     {
-        if (Url::fromPath($value)->isExternal()) {
+        if (Url::fromPath($value)->getRelativeUrl() === '') {
             $this->_error('IS_EXTERNAL');
 
             return false;