diff -u b/core/lib/Drupal/Core/Routing/UrlGenerator.php b/core/lib/Drupal/Core/Routing/UrlGenerator.php
--- b/core/lib/Drupal/Core/Routing/UrlGenerator.php
+++ b/core/lib/Drupal/Core/Routing/UrlGenerator.php
@@ -159,7 +159,6 @@
    */
   public function generateFromRoute($name, $parameters = array(), $options = array()) {
     $options += array('prefix' => '');
-    $absolute = !empty($options['absolute']);
     $route = $this->getRoute($name);
     $this->processRoute($name, $route, $parameters);
 
@@ -170,6 +169,9 @@
 
     $path = $this->getInternalPathFromRoute($route, $parameters);
     $path = $this->processPath($path, $options);
+
+    $absolute = !empty($options['absolute']);
+
     if (!empty($options['prefix'])) {
       $path = ltrim($path, '/');
       $prefix = empty($path) ? rtrim($options['prefix'], '/') : $options['prefix'];
@@ -184,7 +186,7 @@
     }
 
     $base_url = isset($options['base_url']) ? $options['base_url'] : $this->context->getBaseUrl();
-    if (!$absolute || !$host = $this->context->getHost()) {
+    if (!$absolute || preg_match('/^http(s)?\:\\/\//', $base_url) === 1 || !$host = $this->context->getHost()) {
       return $base_url . $path . $fragment;
     }