[racket] red underline of language name

In #lang scribble/manual, if I type

@codeblock{
#lang racket
}

the output (in HTML) has the word "racket" underlined, which seems
fair enough; ditto for

@codeblock{
#lang typed/racket
}

But if I type

@codeblock{
#lang planet foo/bar
}

only the word "planet" is underlined, which seems odd ("planet" is not
the name of the language; the analog of "racket" should be either
"planet foo/bar" or "foo/bar" but not "planet").

Shriram