[racket] integer-sqrt

Hi all,

according to the documentation, the above procedure accepts a *number* 
and returns an integer.

But (at least in Racket 6.1) there's an error message stating that the 
parameter needs to be an *integer*:

---------------------------------------
  > (integer-sqrt 151.29)
   integer-sqrt: contract violation
   expected: integer?
   given: 151.29
---------------------------------------

Is this an error in the documentation or in the implementation?

Regards,
-Patrick