diff --git a/collects/syntax/private/stxparse/rep.ss b/collects/syntax/private/stxparse/rep.ss
index f8e2e99957..f487b7dee3 100644
--- a/collects/syntax/private/stxparse/rep.ss
+++ b/collects/syntax/private/stxparse/rep.ss
@@ -689,6 +689,10 @@
     [(cons (list '#:fail-unless fu-stx unless-condition expr) rest)
      (cons (make clause:fail #`(not #,unless-condition) expr)
            (parse-pattern-sides rest decls))]
+    [(cons (list '#:when unless-condition) rest)
+     ;; Bleh: when is basically fail-unless without the msg argument
+     (cons (make clause:fail #`(not #,unless-condition) #'#f)
+           (parse-pattern-sides rest decls))]
     [(cons (list '#:with with-stx pattern expr) rest)
      (let-values ([(decls2 rest) (grab-decls rest decls)])
        (let-values ([(decls2a defs) (decls-create-defs decls2)])
@@ -876,6 +880,7 @@
   (list (list '#:declare check-identifier check-expression)
         (list '#:fail-when check-expression check-expression)
         (list '#:fail-unless check-expression check-expression)
+        (list '#:when check-expression)
         (list '#:with check-expression check-expression)
         (list '#:attr check-attr-arity check-expression)))
 
diff --git a/collects/syntax/scribblings/parse.scrbl b/collects/syntax/scribblings/parse.scrbl
index bd2910e358..cda0b8ae2c 100644
--- a/collects/syntax/scribblings/parse.scrbl
+++ b/collects/syntax/scribblings/parse.scrbl
@@ -603,7 +603,8 @@ conditions. The grammar for pattern directives follows:
                (code:line #:with syntax-pattern expr)
                (code:line #:attr attr-id expr)
                (code:line #:fail-when condition-expr message-expr)
-               (code:line #:fail-unless condition-expr message-expr)]
+               (code:line #:fail-unless condition-expr message-expr)
+               (code:line #:when condition-expr)]
 
 @specsubform[(code:line #:declare pvar-id syntax-class-id)]
 @specsubform[(code:line #:declare pvar-id (syntax-class-id expr ...))]{
@@ -650,6 +651,15 @@ given message); otherwise, it continues.
 
 }
 
+@specsubform[(code:line #:when condition-expr)]{
+
+Evaluates the @scheme[condition-expr] in the context of all previous
+attribute bindings. If the value is @scheme[#f], the matching process
+backtracks. In other words, @scheme[#:when] is like
+@scheme[#:fail-unless] without the message argument.
+
+}
+
 @deftogether[[
 @defidform[~or]
 @defidform[~and]