Hello, I've been experiencing, for quite some time, now, read/write conflicts in my projects. I've decided to hunt the problem down and it brought me down to the field validation in zope.schema. My use case is the following : class SomeAdapter(object): my_object = FieldProperty(ISomeInterface['my_object']) def __init__(self, context): self.my_object = context If "my _object" from ISomeInterface is an Object field and has a 'schema' property, zope.schema will validate it. The validation code writes an attribute on the value that is being validated and therefore can create a read/write error. The incriminated code is here : http://svn.zope.org/zope.schema/trunk/src/zope/schema/_field.py?rev=111614&r... In my case, the value was an OOBTree and that caused a lot of read/write errors. Can we do something about this validation code ? Could it be a possible solution to change the "__validating_schema" attribute into a _v_ attribute, to avoid the persistency ? Thank you for reading me. - Souheil