diff -u b/core/lib/Drupal/Component/Utility/SafeMarkup.php b/core/lib/Drupal/Component/Utility/SafeMarkup.php
--- b/core/lib/Drupal/Component/Utility/SafeMarkup.php
+++ b/core/lib/Drupal/Component/Utility/SafeMarkup.php
@@ -194,9 +194,9 @@
    *       self::checkPlain() as part of that.
    *     - Some other special reason for suppressing sanitization.
    *   - :variable: Reserved for URL values only. For now, the sanitization
-   *     behavior is the same as !variable, so only use it for URLs that
-   *     have already been filtered for dangerous protocols or are otherwise
-   *     known to not contain them (e.g., if generated from a route). See
+   *     behavior is the same as !variable, so only use it for URLs that have
+   *     already been filtered for dangerous protocols or are otherwise known
+   *     to not contain them (e.g., if generated from a route). See
    *     https://www.drupal.org/node/2565895 about adding automatic protocol
    *     sanitization.
    *