diff --git a/collects/framework/specs.ss b/collects/framework/specs.ss
index fe8da20..8d18af9 100644
--- a/collects/framework/specs.ss
+++ b/collects/framework/specs.ss
@@ -504,7 +504,7 @@
            false? any? 
            union symbols
            subclass?/c implementation?/c is-a?/c
-           listof vectorof
+           listof vectorof cons/p
 	   mixin-contract make-mixin-contract/<%> make-mixin-contract/%)
   
   (define-syntax (name stx)
@@ -567,11 +567,17 @@
                  (andmap p v)))))
   
   (define (vectorof p)
-    (name vectorof 
+    (name vectorof
           (lambda (v)
             (and (vector? v)
                  (andmap p (vector->list v))))))
 
+  (define (cons/p hdp tlp)
+    (lambda (x)
+      (and (pair? x)
+	   (hdp (car x))
+	   (tlp (cdr x)))))
+
   (define mixin-contract
     (class?
      . ->d .