Support plan

• which support plan is this issue covered by? (e.g. Community, Core, Plus, or Enterprise): Communtiy
• is this issue currently blocking your project? (yes/no): no
• is this issue affecting a production system? (yes/no): no

Context

• node version: 12.16.1
• module version with issue: 17.1.0
• last module version without issue: N/A
• environment (e.g. node, browser, native): node
• used with (e.g. hapi application, another framework, standalone, ...): standalone
• any other relevant information: N/A

What are you trying to achieve or the steps to reproduce?

I'm extending a schema with a complex array base:

const custom = Joi.extend({
    type: 'test',
    base: Joi.array().items(Joi.string().required());
});

const schema = custom.test();

schema.validate(['x']); // No errors

const description = schema.describe(); 
const newSchema = custom.build(description);

newSchema.validate(['x']); // "value" does not contain 1 required value(s)

What was the result you got?

A validation error on what is supposed to be valid

What result did you expect?

No error.