[racket] Problem with get-slides-as-picts

I'm using the simple "Hello, World" slideshow from the docs:

#lang slideshow

(slide
 #:title "How to Say Hello"
 (t "Hello World!"))

When I run get-slides-as-picts, I get the following error:

> (get-slides-as-picts "simple-slide.rkt" 1024 768 false)
send: target is not an object: #f for method: glyph-exists?

What am I doing wrong?

Justin