w3m-view-header vs. charset

[jidanni@xxxxxxxxxxx]

In emacs-w3m "=" shows
W3m-current-url: http://www.sciict.com/Chinese/index.htm
W3m-document-charset: US-ASCII
In real w3m, = shows
Document Charset     [Chinese (EUC-CN, GB2312)    ]
                     [Change]