enforcer and unCheckedPluginsList

[nicolas de loof]

I'm trying to configure the enforcer plugin rule "RequiresPluginVersion" to
ignore some plugin I'm using from command line.
I tried to use unCheckedPluginsList as decribe in doc :

                <requirePluginVersions>
                  <message>Always define plugin versions!</message>
                  <banSnapshots>false</banSnapshots>
                  <unCheckedPluginsList>foo:bar</unCheckedPluginsList>
                </requirePluginVersions>
, but get thir error :

[INFO] Failed to configure plugin parameters for:
org.apache.maven.plugins:maven
-enforcer-plugin:1.0-beta-1

Cause: Cannot find setter nor field in
org.apache.maven.plugins.enforcer.Require
PluginVersions for 'unCheckedPluginsList'

Any idea ?