diff --git a/core/lib/Drupal/Core/Template/TwigExtension.php b/core/lib/Drupal/Core/Template/TwigExtension.php
index 52291c3..e0cd126 100644
--- a/core/lib/Drupal/Core/Template/TwigExtension.php
+++ b/core/lib/Drupal/Core/Template/TwigExtension.php
@@ -541,14 +541,14 @@ public function renderVar($arg) {
    *   This value is expected to be safe for output and user provided data
    *   should never be used as a glue.
    *
-   * @return string
-   *   The strings joined together.
+   * @return TwigMarkup
+   *   The created imploded string, which is now markup.
    */
   public function safeJoin(\Twig_Environment $env, $value, $glue = '') {
-    return implode($glue, array_map(function($item) use ($env) {
+    return new TwigMarkup(implode($glue, array_map(function($item) use ($env) {
       // If $item is not marked safe then it will be escaped.
       return $this->escapeFilter($env, $item, 'html', NULL, TRUE);
-    }, $value));
+    }, $value)), $env->getCharset());
   }
 
 }
diff --git a/core/lib/Drupal/Core/Template/TwigMarkup.php b/core/lib/Drupal/Core/Template/TwigMarkup.php
new file mode 100644
index 0000000..d642183
--- /dev/null
+++ b/core/lib/Drupal/Core/Template/TwigMarkup.php
@@ -0,0 +1,36 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Template\TwigMarkup.
+ */
+
+namespace Drupal\Core\Template;
+
+use Drupal\Component\Render\MarkupInterface;
+
+/**
+ * A class that defines Twig markup class for Drupal.
+ */
+class TwigMarkup extends \Twig_Markup implements MarkupInterface {
+
+  /**
+   * Constructs an TwigMarkup object.
+   *
+   * @param string $string
+   *   The string containing markup to wrap as an object.
+   * @param string $charset
+   *   The character set used when counting, defaulted to utf-8 for convenience.
+   */
+  public function __construct($string, $charset = 'utf-8') {
+    parent::__construct($string, $charset);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function jsonSerialize() {
+    return $this->__toString();
+  }
+
+}
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index efa1f5c..ba725bf 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -211,8 +211,7 @@ function template_preprocess_system_modules_details(&$variables) {
     $module['id'] = $id;
     $module['enable_id'] = $module['enable']['#id'];
 
-    // @todo Remove early rendering and use safe_join in the Twig template once
-    //   https://www.drupal.org/node/2579091 is fixed.
+    // @todo Remove early rendering.
     $renderer = \Drupal::service('renderer');
     $machine_name_render = [
       '#prefix' => '<span dir="ltr" class="table-filter-text-source">',
@@ -222,20 +221,10 @@ function template_preprocess_system_modules_details(&$variables) {
     $module['machine_name'] = $renderer->render($machine_name_render);
 
     if (!empty($module['#requires'])) {
-      $requires = [
-        '#theme' => 'item_list',
-        '#items' => $module['#requires'],
-        '#context' => ['list_style' => 'comma-list'],
-      ];
-      $module['requires'] = $renderer->render($requires);
+      $module['requires'] = $module['#requires'];
     }
     if (!empty($module['#required_by'])) {
-      $required_by = [
-        '#theme' => 'item_list',
-        '#items' => $module['#required_by'],
-        '#context' => ['list_style' => 'comma-list'],
-      ];
-      $module['required_by'] = $renderer->render($required_by);
+      $module['required_by'] = $module['#required_by'];
     }
 
     if (!empty($module['version'])) {
diff --git a/core/modules/system/templates/system-modules-details.html.twig b/core/modules/system/templates/system-modules-details.html.twig
index e431c8e..5ad7812 100644
--- a/core/modules/system/templates/system-modules-details.html.twig
+++ b/core/modules/system/templates/system-modules-details.html.twig
@@ -53,10 +53,10 @@
                     <div class="admin-requirements">{{ 'Version: @module-version'|t({'@module-version': module.version }) }}</div>
                   {% endif %}
                   {% if module.requires %}
-                    <div class="admin-requirements">{{ 'Requires: @module-list'|t({'@module-list': module.requires }) }}</div>
+                    <div class="admin-requirements">{{ 'Requires: @module-list'|t({'@module-list': module.requires|safe_join(', ') }) }}</div>
                   {% endif %}
                   {% if module.required_by %}
-                    <div class="admin-requirements">{{ 'Required by: @module-list'|t({'@module-list': module.required_by }) }}</div>
+                    <div class="admin-requirements">{{ 'Required by: @module-list'|t({'@module-list': module.required_by|safe_join(', ') }) }}</div>
                   {% endif %}
                 </div>
                 {% if module.links %}
diff --git a/core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php b/core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php
index 6b9525e..f20607d 100644
--- a/core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php
+++ b/core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Tests\Core\Template;
 
+use Drupal\Component\Render\FormattableMarkup;
 use Drupal\Core\Render\RenderableInterface;
 use Drupal\Core\Render\RendererInterface;
 use Drupal\Core\StringTranslation\TranslatableMarkup;
@@ -200,6 +201,11 @@ public function testSafeJoin() {
     ];
     $result = $twig_extension->safeJoin($twig_environment, $items, '<br/>');
     $this->assertEquals('&lt;em&gt;will be escaped&lt;/em&gt;<br/><em>will be markup</em><br/><strong>will be rendered</strong>', $result);
+
+    // Ensure that result of safe join can be used in t() and string formatting
+    // without double escaping.
+    $result = new FormattableMarkup('Kittens @text', ['@text' => $result]);
+    $this->assertEquals('Kittens &lt;em&gt;will be escaped&lt;/em&gt;<br/><em>will be markup</em><br/><strong>will be rendered</strong>', $result);
   }
 
   /**