Update of XML value with xmlstarlet

I have file config.xml:

App title
    Dummy dummy text.

I'd like to change value of `` element. I've tried following:

xmlstarlet edit -L -u "/_:widget/name" -v "NEW_NAME" config.xml

and

xmlstarlet edit -L -u "//name" -v "NEW_NAME" config.xml

But it hasn't changed the App title value.