apiary authentication description not work?

Question

I currently have this blueprint as https://help.apiary.io/api_101/apib-authentication/#describing-basic-auth-in-api-blueprint described.

FORMAT: 1A

# Basic Auth API

## Basic Auth protected resource [/protected]

### Status [GET]
+ Response 401
    + Headers

            WWW-Authenticate: Basic realm="protected"

+ Request
    + Headers

            Authorization: Basic dTE6dDE=

+ Response 200 (application/json)

            {
                "status": "ok"
            }

But it won't work, the api endpoint would pop up asking for username/pwd and I entered the corresponding pair u1:p1 it will just pop up the window again. Does anyone have insight on this? Thanks so much in advance!