diff --git a/core/lib/Drupal/Component/Datetime/DateTimePlus.php b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
index f5c3cc7..283daae 100644
--- a/core/lib/Drupal/Component/Datetime/DateTimePlus.php
+++ b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
@@ -710,7 +710,7 @@ public function format($format, $settings = array()) {
 
         // If we're working with a non-gregorian calendar, indicate that.
         $calendar_type = \IntlDateFormatter::GREGORIAN;
-        if ($calendar != SELF::CALENDAR) {
+        if ($calendar != self::CALENDAR) {
           $calendar_type = \IntlDateFormatter::TRADITIONAL;
         }