diff --git a/snappymail/v/0.0.0/app/libraries/MailSo/Imap/Enumerations/FetchType.php b/snappymail/v/0.0.0/app/libraries/MailSo/Imap/Enumerations/FetchType.php
index f3388cd57..ad45b0591 100644
--- a/snappymail/v/0.0.0/app/libraries/MailSo/Imap/Enumerations/FetchType.php
+++ b/snappymail/v/0.0.0/app/libraries/MailSo/Imap/Enumerations/FetchType.php
@@ -56,6 +56,8 @@ abstract class FetchType
 	// RFC 8474
 	const EMAILID = 'EMAILID';
 	const THREADID = 'THREADID';
+	// RFC 8970
+	const PREVIEW = 'PREVIEW';
 
 	public static function BuildBodyCustomHeaderRequest(array $aHeaders, bool $bPeek = true) : string
 	{