[Taxonomy] Missing crucial step in documentation about adding the classifiable mixin

In page http://taxonomy.forge.onehippo.org/cms-configuration.html , halfway, it instructs to add the mixin hippotaxonomy:classifiable to your document type, in your cnd.

This is not enough, you need to add the mixin to your document type's prototypes as well. If you don't, you get the following exception:

Caused by: java.lang.IllegalStateException: node with path /content/documents/myhippoproject/common/test/test is not classifiable
[INFO] [talledLocalContainer] at org.onehippo.taxonomy.plugin.MixinClassificationDaoPlugin.getClassification(MixinClassificationDaoPlugin.java:69)
[INFO] [talledLocalContainer] at org.onehippo.taxonomy.plugin.TaxonomyPickerPlugin$CategoryListView.getItemModels(TaxonomyPickerPlugin.java:88)
[INFO] [talledLocalContainer] at org.apache.wicket.markup.repeater.RefreshingView.onPopulate(RefreshingView.java:94)
[INFO] [talledLocalContainer] at org.apache.wicket.markup.repeater.AbstractRepeater.onBeforeRender(AbstractRepeater.java:131)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.internalBeforeRender(Component.java:1069)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.beforeRender(Component.java:1103)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.onBeforeRenderChildren(MarkupContainer.java:1777)
[INFO] [talledLocalContainer] ... 72 more

The above happens when you start with a clean repository and follow the steps in the documentation (http://taxonomy.forge.onehippo.org/cms-configuration.html)

I'm also wondering what happens with existing documents of a type to which taxonomy field was added later. This actually gives an error about non trivial cnd changes, see my last comment.

Can someone verify this? Then I'll proceed and correct the documentation.