diff --git a/collects/teachpack/htdp/scribblings/image.scrbl b/collects/teachpack/htdp/scribblings/image.scrbl
index b9ff0c5e68..391b30df4d 100644
--- a/collects/teachpack/htdp/scribblings/image.scrbl
+++ b/collects/teachpack/htdp/scribblings/image.scrbl
@@ -93,7 +93,9 @@ angle.
 
 @defproc[(text [s string?] [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].}
+ and painted in color @scheme[c].
+ 
+ The string @scheme[s] must have at least one character.}
 
 @;-----------------------------------------------------------------------------
 @section[#:tag "properties"]{Basic Image Properties}