diff --git a/INSTALL b/INSTALL
index 29d37d2b0..7acb520a1 100644
--- a/INSTALL
+++ b/INSTALL
@@ -26,6 +26,7 @@ REQUIREMENTS
    - Net_Sieve 1.4.3 or newer (for managesieve plugin)
    - Crypt_GPG 1.6.3 or newer (for enigma plugin)
    - Endroid/QrCode 1.6.0 or newer (https://github.com/endroid/QrCode)
+   - Kolab/Net_LDAP3 1.0.6 or newer (for LDAP addressbook)
 * php.ini options:
    - error_reporting E_ALL & ~E_NOTICE & ~E_STRICT
    - memory_limit > 16MB
diff --git a/program/lib/Roundcube/README.md b/program/lib/Roundcube/README.md
index 1e028a3be..e0d202cc6 100644
--- a/program/lib/Roundcube/README.md
+++ b/program/lib/Roundcube/README.md
@@ -29,13 +29,14 @@ INSTALLATION
 ------------
 Copy all files of this directory to your project or install it in the default
 include_path directory of your webserver. Some classes of the framework require
-one or multiple of the following [PEAR][pear] libraries:
+following [PEAR][pear] libraries:
 
 - Mail_Mime 1.8.1 or newer
 - Net_SMTP 1.8.1 or newer
 - Net_Socket 1.0.12 or newer
 - Net_IDNA2 0.1.1 or newer
 - Auth_SASL 1.0.6 or newer
+- Kolab/Net_LDAP3 1.0.6 or newer (for LDAP addressbook)
 
 
 USAGE