diff --git a/collects/scribblings/guide/namespaces.scrbl b/collects/scribblings/guide/namespaces.scrbl
index fc47aacd5f..d387458d94 100644
--- a/collects/scribblings/guide/namespaces.scrbl
+++ b/collects/scribblings/guide/namespaces.scrbl
@@ -270,7 +270,7 @@ first be used to evaluate any top-level expression---not even
 fails, because the namespace does not include the primitive modules on
 which @racket[racket] is built.
 
-To make a namespace useful, some modules much be @deftech{attached}
+To make a namespace useful, some modules must be @deftech{attached}
 from an existing namespace. Attaching a module adjusts the mapping of
 module names to instances by transitively copying entries (the module
 and all its imports) from an existing namespace's mapping. Normally,