diff --git a/program/actions/mail/show.php b/program/actions/mail/show.php
index 720230ea273..4b831754838 100644
--- a/program/actions/mail/show.php
+++ b/program/actions/mail/show.php
@@ -486,7 +486,7 @@ public static function message_headers($attrib, $headers = null)
             } elseif (in_array($hkey, ['from', 'to', 'cc', 'bcc'])) {
                 $header_value = self::address_string($value, $attr_max, true, $attr_addicon, $charset, $header_title);
                 $ishtml = true;
-            } elseif ($hkey == 'subject' && empty($value)) {
+            } elseif ($hkey == 'subject' && empty($value)) { // @phpstan-ignore-line
                 $header_value = $rcmail->gettext('nosubject');
             } else {
                 $value = is_array($value) ? implode(' ', $value) : $value;