diff --git a/collects/scribblings/reference/evts.scrbl b/collects/scribblings/reference/evts.scrbl
index 87bd36aab0..c612ed52a5 100644
--- a/collects/scribblings/reference/evts.scrbl
+++ b/collects/scribblings/reference/evts.scrbl
@@ -197,7 +197,7 @@ with timeouts that have not yet expired. The system-idle event's
 @racket[system-idle-evt] procedure is always the same event.}
 
 
-@defproc[(alarm-evt [msecs nonnegative-number?]) evt]{
+@defproc[(alarm-evt [msecs (>=/c 0)]) evt?]{
 
 Returns a @tech{synchronizable event} that is not @tech{ready for synchronization} when
 @racket[(current-inexact-milliseconds)] would return a value that is