Response: {"error_msg":"Library password is needed."}

Recently i created a new user with web API 2.1 and through API, i also created an encrypted library using a password like md5 Hash. library was created successfully. But later on. when i tried to fetch library using password. it goes like this

Message: Client error: POST http://xxxxxxxxxxxxxxxxxxx/api2/repos/lib_id/?password=lib_password resulted in a 440 Unknown Status Code response: {“error_msg”:“Library password is needed.”}

And without giving password, it works fine on encrypted library. in seafile server, it needs password to unlock the library, but in API it works only without password.
Any one knows, whats going on ?
Any help will be appreciated.