[racket] 'Single-Flonum' error in Typed Racket

Running this program in DrRacket...

#lang typed/racket
(provide (all-defined-out))
(: foo Single-Flonum)
(define foo 1.0f0)

...gives me this error:

expand: unbound identifier in module in: t:single-flonum?

I don't know what it means or why it shows up when I try to provide
all-defined-out. I've tried replacing Single-Flonum with various other
types, and it seems to be the only one affected. For example, using
Positive-Single-Flonum doesn't result in this error.