diff --git a/collects/teachpack/htdp/scribblings/image.scrbl b/collects/teachpack/htdp/scribblings/image.scrbl
index 391b30df4d..7d629859a0 100644
--- a/collects/teachpack/htdp/scribblings/image.scrbl
+++ b/collects/teachpack/htdp/scribblings/image.scrbl
@@ -91,7 +91,7 @@ angle.
  See @scheme[add-line] below.
 }
 
-@defproc[(text [s string?] [f (and/c number? positive?)] [c (unsyntax @tech{Color})]) Image]{
+@defproc[(text [s (and/c string? (lambda (s) (not (string=? s ""))))] [f (and/c number? positive?)] [c (unsyntax @tech{Color})]) Image]{
  Creates an image of the text @scheme[s] at point size @scheme[f] 
  and painted in color @scheme[c].