diff --git a/xenomorph/xenomorph/list.rkt b/xenomorph/xenomorph/list.rkt
index d6ec2d0e..ca3ebd7e 100644
--- a/xenomorph/xenomorph/list.rkt
+++ b/xenomorph/xenomorph/list.rkt
@@ -114,10 +114,10 @@ https://github.com/mbutterick/restructure/blob/master/src/Array.coffee
    x:list?)
   (define type (or type-arg type-kwarg))
   (unless (xenomorphic? type)
-    (raise-argument-error x:list "xenomorphic type" type))
+    (raise-argument-error 'x:list "xenomorphic type" type))
   (define len (or len-arg len-kwarg))
   (unless (length-resolvable? len)
-    (raise-argument-error x:list "resolvable length" len))
+    (raise-argument-error 'x:list "resolvable length" len))
   (new (generate-subclass base-class pre-proc post-proc)
        [type type]
        [len len]
diff --git a/xenomorph/xenomorph/stream.rkt b/xenomorph/xenomorph/stream.rkt
index 05914b60..b23659da 100644
--- a/xenomorph/xenomorph/stream.rkt
+++ b/xenomorph/xenomorph/stream.rkt
@@ -61,10 +61,10 @@ https://github.com/mbutterick/restructure/blob/master/src/LazyArray.coffee
    x:stream?)
   (define type (or type-arg type-kwarg))
     (unless (xenomorphic? type)
-    (raise-argument-error x:stream "xenomorphic type" type))
+    (raise-argument-error 'x:stream "xenomorphic type" type))
   (define len (or len-arg len-kwarg))
    (unless (length-resolvable? len)
-    (raise-argument-error x:stream "resolvable length" len))
+    (raise-argument-error 'x:stream "resolvable length" len))
   (new (generate-subclass base-class pre-proc post-proc) [type type]
        [len len]
        [count-bytes? #false]))
diff --git a/xenomorph/xenomorph/vector.rkt b/xenomorph/xenomorph/vector.rkt
index 9367790e..d9bc34b0 100644
--- a/xenomorph/xenomorph/vector.rkt
+++ b/xenomorph/xenomorph/vector.rkt
@@ -1,5 +1,6 @@
 #lang debug racket/base
 (require racket/class
+         racket/contract
          "base.rkt"
          "number.rkt"
          "util.rkt"
@@ -18,19 +19,39 @@
     
     (define/override (post-decode val) (list->vector val))))
 
-(define (x:vector [type-arg #f] [len-arg #f] [length-type-arg 'count]
-                 #:type [type-kwarg #f]
-                 #:length [len-kwarg #f]
-                 #:count-bytes [count-bytes? #f]
-                 #:pre-encode [pre-proc #f]
-                 #:post-decode [post-proc #f]
-                 #:base-class [base-class x:vector%])
-  (new (generate-subclass base-class pre-proc post-proc) [type (or type-arg type-kwarg)]
-       [len (or len-arg len-kwarg)]
-       [count-bytes? count-bytes?]))
-
 (define (x:vector? x) (is-a? x x:vector%))
 
+(define/contract (x:vector
+                  [type-arg #f]
+                  [len-arg #f]
+                  #:type [type-kwarg #f]
+                  #:length [len-kwarg #f]
+                  #:count-bytes [count-bytes? #f]
+                  #:pre-encode [pre-proc #f]
+                  #:post-decode [post-proc #f]
+                  #:base-class [base-class x:vector%])
+  (()
+   ((or/c xenomorphic? #false)
+    (or/c length-resolvable? #false)
+    #:type (or/c xenomorphic? #false)
+    #:length (or/c length-resolvable? #false)
+    #:count-bytes boolean?
+    #:pre-encode (or/c (any/c . -> . any/c) #false)
+    #:post-decode (or/c (any/c . -> . any/c) #false)
+    #:base-class (λ (c) (subclass? c x:vector%)))
+   . ->* .
+   x:vector?)
+  (define type (or type-arg type-kwarg))
+  (unless (xenomorphic? type)
+    (raise-argument-error 'x:vector "xenomorphic type" type))
+  (define len (or len-arg len-kwarg))
+  (unless (length-resolvable? len)
+    (raise-argument-error 'x:vector "resolvable length" len))
+  (new (generate-subclass base-class pre-proc post-proc)
+       [type type]
+       [len len]
+       [count-bytes? count-bytes?]))
+
 (module+ test
   (require rackunit)
   (check-equal? (decode (x:vector uint16be 3) #"ABCDEF") '#(16706 17220 17734))