diff -u b/core/modules/system/system.install b/core/modules/system/system.install
--- b/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -112,7 +112,7 @@
       '@system_requirements' => 'http://drupal.org/requirements',
     ));
 
-    // We use twig inline_template to avoid double escaping.
+    // We use twig inline_template to avoid twig's autoescape.
     $description = array(
       '#type' => 'inline_template',
       '#template' => '{{ description }}{{ missing_extensions }}',
@@ -196,7 +196,7 @@
   );
 
   if (!Environment::checkMemoryLimit(DRUPAL_MINIMUM_PHP_MEMORY_LIMIT, $memory_limit)) {
-    $description = '';
+    $description = array();
     if ($phase == 'install') {
       $description['phase'] = t('Consider increasing your PHP memory limit to %memory_minimum_limit to help prevent errors in the installation process.', array('%memory_minimum_limit' => DRUPAL_MINIMUM_PHP_MEMORY_LIMIT));
     }
@@ -443,12 +443,12 @@
       }
       if (!empty($description)) {
         $description = array(
-         '#type' => 'inline_template',
-         '#template' => '{{ error }} {{ description }}',
-         '#context' => array(
-           'error' => $error,
-           'description' => $description,
-         ),
+          '#type' => 'inline_template',
+          '#template' => '{{ error }} {{ description }}',
+          '#context' => array(
+            'error' => $error,
+            'description' => $description,
+          ),
         );
         $requirements['file system']['description'] = $description;
         $requirements['file system']['severity'] = REQUIREMENT_ERROR;