diff --git a/core/lib/Drupal/Core/Mail/MailFormatHelper.php b/core/lib/Drupal/Core/Mail/MailFormatHelper.php
index 7be6e45..1df3de1 100644
--- a/core/lib/Drupal/Core/Mail/MailFormatHelper.php
+++ b/core/lib/Drupal/Core/Mail/MailFormatHelper.php
@@ -129,7 +129,7 @@ public static function htmlToText($string, $allowed_tags = NULL) {
     // 'See the Drupal site [1]' with the URL included as a footnote.
     self::htmlToMailUrls(NULL, TRUE);
     $pattern = '@(<a[^>]+?href="([^"]*)"[^>]*?>(.+?)</a>)@i';
-    $string = preg_replace_callback($pattern, '_drupal_html_to_mail_urls', $string);
+    $string = preg_replace_callback($pattern, 'self::htmlToMailUrls', $string);
     $urls = self::htmlToMailUrls();
     $footnotes = '';
     if (count($urls)) {