diff --git a/docs/simplesamlphp-install.txt b/docs/simplesamlphp-install.txt
index 76a5fb4d8c9dba39ec530fcae63adcd1549b3de5..9149673644150d607e2b671a2722352cec173050 100644
--- a/docs/simplesamlphp-install.txt
+++ b/docs/simplesamlphp-install.txt
@@ -34,7 +34,8 @@ Prerequisites
  * Some webserver capable of executing PHP scripts.
  * PHP version >= 5.3.0.
  * Support for the following PHP extensions:
-   * Always required: `date`, `dom`, `hash`, `libxml`, `openssl`, `pcre`, `SPL`, `zlib`, `mcrypt`
+   * Always required: `date`, `dom`, `hash`, `libxml`, `openssl`, `pcre`, `SPL`, `zlib`
+   * When using encryption or digital signatures: `mcrypt`
    * When authenticating against LDAP server: `ldap`
    * When authenticating against RADIUS server: `radius`
    * When saving session information to memcache-server: `memcache`
diff --git a/modules/core/www/frontpage_config.php b/modules/core/www/frontpage_config.php
index 74c8c61fa16e62d759e431b34ccdb0fda2955056..d04beaf6058e4760e0687e65446282ac2797ce39 100644
--- a/modules/core/www/frontpage_config.php
+++ b/modules/core/www/frontpage_config.php
@@ -85,7 +85,7 @@ $functionchecks = array(
 	'simplexml_import_dom' => array('required', 'SimpleXML'),
 	'dom_import_simplexml' => array('required', 'XML DOM'),
 	'preg_match'       => array('required',  'RegEx support'),
-	'mcrypt_module_open'=> array('required',  'MCrypt'),
+	'mcrypt_module_open'=> array('optional',  'MCrypt'),
 	'mysql_connect'    => array('optional',  'MySQL support'),
 );
 if (SimpleSAML_Module::isModuleEnabled('ldap')) {