Problem with custom schema.xml for defining FeatureType

The problem arised when configuring a feature type with a custom schema.xml file.

I follow the procedure explained in the documentation, in page "Geoserver config files": I have a PostGIS table in my datastore, I don't create the FeatureType with the web admin but create a directory with the proper name in the data directory, then put into it the info.xml and schema.xml files (handwritten), with a custom GML Schema. Then I open Geoserver's web admin and hit "Load". All works fine: it loads the new configuration, I can see the new feature type and the WFS DescribeFeatureType request returns the right schema. I tested the WMS and WFS interfaces on these datas and all works perfectly, so I'm confident my info.xml and schema.xml files are correct.

Then I use the web admin to edit another already existent feature type (I change a trivial parameter, like the bounding box), hit "Apply", then "Save". Geoserver takes the new parameter correctly, but my custom schema.xml file is rewritten. If I repeat the DescribeFeatureType request I still get the correct result, but only because Geoserver has it in some cache: if I hit "Load" or restart Tomcat, the response gets corrupted.