diff --git a/core/lib/Drupal/Core/Template/TwigExtension.php b/core/lib/Drupal/Core/Template/TwigExtension.php
index f11fe67..4937b5a 100644
--- a/core/lib/Drupal/Core/Template/TwigExtension.php
+++ b/core/lib/Drupal/Core/Template/TwigExtension.php
@@ -142,7 +142,7 @@ public function getFilters() {
       // Implements safe joining.
       // @todo Make that the default for |join? Upstream issue:
       //   https://github.com/fabpot/Twig/issues/1420
-      new \Twig_SimpleFilter('safe_join', array($this, 'safeJoin'), array('needs_environment' => true, 'is_safe' => array('html'))),
+      new \Twig_SimpleFilter('safe_join', [$this, 'safeJoin'], ['needs_environment' => true, 'is_safe' => ['html']]),
 
       // Array filters.
       new \Twig_SimpleFilter('without', 'twig_without'),
@@ -530,14 +530,10 @@ public function renderVar($arg) {
    *   The imploded string.
    */
   public function safeJoin(\Twig_Environment $env, $value, $glue = '') {
-    $separator = '';
-    $output = '';
-    foreach ($value as $item) {
+    return implode($glue, array_map(function($item) use ($env) {
       // If $item is not marked safe then it will be escaped.
-      $output .= $separator . $this->escapeFilter($env, $item, 'html', NULL, TRUE);
-      $separator = $glue;
-    }
-    return $output;
+      return $this->escapeFilter($env, $item, 'html', NULL, TRUE);
+    }, $value));
   }
 
 }