undefined method `password' for #<UserSession: no credentials provided>

Extracted source (around line #9):

6:   <%= f.text_field :login %><br />
7:   <br />
8:   <%= f.label :password %><br />
9:   <%= f.password_field :password %><br />
10:   <br />
11:   <%= f.check_box :remember_me %><%= f.label :remember_me %><br />
12:   <br />