diff --git a/plugins/LdapAuthorization/LdapAuthorizationPlugin.php b/plugins/LdapAuthorization/LdapAuthorizationPlugin.php
index cf1347bed0..69357f8aad 100644
--- a/plugins/LdapAuthorization/LdapAuthorizationPlugin.php
+++ b/plugins/LdapAuthorization/LdapAuthorizationPlugin.php
@@ -48,7 +48,7 @@ class LdapAuthorizationPlugin extends AuthorizationPlugin
     public $scope=null;
     public $provider_name = null;
     public $uniqueMember_attribute = null;
-    public $roles_to_groups = null;
+    public $roles_to_groups = array();
     public $login_group = null;
     public $attributes = array();
 
@@ -66,9 +66,6 @@ class LdapAuthorizationPlugin extends AuthorizationPlugin
         if(!isset($this->uniqueMember_attribute)){
             throw new Exception("uniqueMember_attribute must be set.");
         }
-        if(!isset($this->roles_to_groups)){
-            throw new Exception("roles_to_groups must be set.");
-        }
         if(!isset($this->attributes['username'])){
             throw new Exception("username attribute must be set.");
         }
diff --git a/plugins/LdapAuthorization/README b/plugins/LdapAuthorization/README
index fcf1efa47e..44239d8e06 100644
--- a/plugins/LdapAuthorization/README
+++ b/plugins/LdapAuthorization/README
@@ -16,7 +16,7 @@ authoritative (false): should this plugin be authoritative for
     authorization?
 uniqueMember_attribute ('uniqueMember')*: the attribute of a group
     that lists the DNs of its members
-roles_to_groups*: array that maps StatusNet roles to LDAP groups
+roles_to_groups: array that maps StatusNet roles to LDAP groups
     some StatusNet roles are: moderator, administrator, sandboxed, silenced
 login_group: if this is set to a group DN, only members of that group will be
     allowed to login