diff --git a/setup/webmail.sh b/setup/webmail.sh
index a41d79d4..eb42a3c4 100755
--- a/setup/webmail.sh
+++ b/setup/webmail.sh
@@ -49,8 +49,8 @@ apt_install php${PHP_VER}-ldap
 #   https://github.com/mstilkerich/rcmcarddav/releases
 # The easiest way to get the package hashes is to run this script and get the hash from
 # the error message.
-VERSION=1.6.1
-HASH=0e1c771ab83ea03bde1fd0be6ab5d09e60b4f293
+VERSION=1.6.4
+HASH=bfc693d6590542d63171e6a3997fc29f0a5f12ca
 PERSISTENT_LOGIN_VERSION=version-5.3.0
 HTML5_NOTIFIER_VERSION=68d9ca194212e15b3c7225eb6085dbcf02fd13d7 # version 0.6.4+
 CARDDAV_VERSION=4.4.3