diff --git a/collects/scribblings/gui/radio-box-class.scrbl b/collects/scribblings/gui/radio-box-class.scrbl
index fd0ac95e3f..8557e22b24 100644
--- a/collects/scribblings/gui/radio-box-class.scrbl
+++ b/collects/scribblings/gui/radio-box-class.scrbl
@@ -4,7 +4,7 @@
 @defclass/title[radio-box% object% (control<%>)]{
 
 
-A @racket[radio-box%] control allows the user to select one of
+A @racket[radio-box%] control allows the user to select one of a
  number of mutually exclusive items. The items are displayed as a
  vertical column or horizontal row of labelled @defterm{radio
  buttons}. Unlike a @racket[list-control<%>], the set of items in a