diff --git a/xenomorph/xenomorph/array.rkt b/xenomorph/xenomorph/array.rkt
index 9bb4d23e..14be6b07 100644
--- a/xenomorph/xenomorph/array.rkt
+++ b/xenomorph/xenomorph/array.rkt
@@ -12,7 +12,7 @@ https://github.com/mbutterick/restructure/blob/master/src/Array.coffee
 |#
 
 (define x:array%
-  (class xenobase%
+  (class x:base%
     (super-new)
     (init-field [(@type type)] [(@len len)] [(@count-bytes? count-bytes?)])
     
diff --git a/xenomorph/xenomorph/base.rkt b/xenomorph/xenomorph/base.rkt
index 3d5c76fb..3743bfd9 100644
--- a/xenomorph/xenomorph/base.rkt
+++ b/xenomorph/xenomorph/base.rkt
@@ -1,5 +1,5 @@
 #lang racket/base
-(require racket/class)
+(require racket/class racket/match)
 (provide (all-defined-out))
 
 (struct x:ptr (type val parent) #:transparent)
@@ -45,7 +45,7 @@
 (define (size xo [val #f] #:parent [parent #f])
   (send xo size val parent))
 
-(define (xenomorphic-type? x) (is-a? x xenobase%))
+(define (xenomorphic-type? x) (is-a? x x:base%))
 (define xenomorphic? xenomorphic-type?)
 
 (define-syntax-rule (generate-subclass CLASS PRE-ENCODE-PROC POST-DECODE-PROC)
@@ -65,7 +65,7 @@
        (define/override (post-decode x) (POST-DECODE-PROC (super post-decode x))))]
     [else CLASS]))
 
-(define xenobase%
+(define x:base%
   (class object%
     (super-new)
     
@@ -73,14 +73,14 @@
       (post-decode (inner (error 'decode-not-augmented) decode input-port parent)))
     
     (define/pubment (encode val output-port [parent #f])
-      (define encode-result (inner (error 'encode-not-augmented) encode (pre-encode val) output-port parent))
-      (when (bytes? encode-result) (write-bytes encode-result output-port)))
+      (match (inner (error 'encode-not-augmented) encode (pre-encode val) output-port parent)
+        [(? bytes? encode-result) (write-bytes encode-result output-port)]
+        [_ (void)]))
     
     (define/pubment (size [val #f] [parent #f] . args)
-      (define asize (inner 0 size val parent . args))
-      (unless (and (integer? asize) (not (negative? asize)))
-        (raise-argument-error 'size "nonnegative integer" asize))
-      asize)
+      (match (inner 0 size val parent . args)
+        [(? exact-nonnegative-integer? size) size]
+        [other (raise-argument-error 'size "nonnegative integer" other)]))
     
     (define/public (post-decode val) val)
     (define/public (pre-encode val) val)))
\ No newline at end of file
diff --git a/xenomorph/xenomorph/bitfield.rkt b/xenomorph/xenomorph/bitfield.rkt
index fd661589..7b77f0fc 100644
--- a/xenomorph/xenomorph/bitfield.rkt
+++ b/xenomorph/xenomorph/bitfield.rkt
@@ -8,7 +8,7 @@ https://github.com/mbutterick/restructure/blob/master/src/Bitfield.coffee
 |#
 
 (define x:bitfield%
-  (class xenobase%
+  (class x:base%
     (super-new)
     (init-field [(@type type)][(@flags flags)])
     (unless (andmap (λ (f) (or (symbol? f) (not f))) @flags)
diff --git a/xenomorph/xenomorph/buffer.rkt b/xenomorph/xenomorph/buffer.rkt
index f1f105a7..111ee667 100644
--- a/xenomorph/xenomorph/buffer.rkt
+++ b/xenomorph/xenomorph/buffer.rkt
@@ -8,7 +8,7 @@ https://github.com/mbutterick/restructure/blob/master/src/Buffer.coffee
 |#
 
 (define x:buffer%
-  (class xenobase%
+  (class x:base%
     (super-new)
     (init-field [(@len len)])
     (unless (length-resolvable? @len)
diff --git a/xenomorph/xenomorph/enum.rkt b/xenomorph/xenomorph/enum.rkt
index de92efb1..88373dbf 100644
--- a/xenomorph/xenomorph/enum.rkt
+++ b/xenomorph/xenomorph/enum.rkt
@@ -8,7 +8,7 @@ https://github.com/mbutterick/restructure/blob/master/src/Enum.coffee
 |#
 
 (define x:enum%
-  (class xenobase%
+  (class x:base%
     (super-new)
     (init-field [(@type type)] [(@values values)])
      
diff --git a/xenomorph/xenomorph/number.rkt b/xenomorph/xenomorph/number.rkt
index d47eaeaa..266c3f69 100644
--- a/xenomorph/xenomorph/number.rkt
+++ b/xenomorph/xenomorph/number.rkt
@@ -24,7 +24,7 @@ https://github.com/mbutterick/restructure/blob/master/src/Number.coffee
 (define system-endian (if (system-big-endian?) 'be 'le))
 
 (define x:number%
-  (class xenobase%
+  (class x:base%
     (super-new)
     (init-field [(@size size)] [(@endian endian)])
     
diff --git a/xenomorph/xenomorph/optional.rkt b/xenomorph/xenomorph/optional.rkt
index 9ac33365..9d28e341 100644
--- a/xenomorph/xenomorph/optional.rkt
+++ b/xenomorph/xenomorph/optional.rkt
@@ -8,7 +8,7 @@ https://github.com/mbutterick/restructure/blob/master/src/Optional.coffee
 |#
 
 (define x:optional%
-  (class xenobase%
+  (class x:base%
     (super-new)
     (init-field [(@type type)] [(@condition condition)])
 
diff --git a/xenomorph/xenomorph/pointer.rkt b/xenomorph/xenomorph/pointer.rkt
index 2c22b706..3ffcb4e5 100644
--- a/xenomorph/xenomorph/pointer.rkt
+++ b/xenomorph/xenomorph/pointer.rkt
@@ -24,7 +24,7 @@ https://github.com/mbutterick/restructure/blob/master/src/Pointer.coffee
     [else (raise-argument-error 'x:pointer "VoidPointer" val)]))
 
 (define x:pointer%
-  (class xenobase%
+  (class x:base%
     (super-new)
     (init-field [(@offset-type offset-type)]
                 [(@type type)]
@@ -113,7 +113,7 @@ https://github.com/mbutterick/restructure/blob/master/src/Pointer.coffee
        [null-value null-value]))
 
 ;; A pointer whose type is determined at decode time
-(define x:void-pointer% (class xenobase%
+(define x:void-pointer% (class x:base%
                          (super-new)
                          (init-field type value)))
 (define (x:void-pointer . args) (apply make-object x:void-pointer% args))
diff --git a/xenomorph/xenomorph/reserved.rkt b/xenomorph/xenomorph/reserved.rkt
index 8e45ef8f..fc5d879b 100644
--- a/xenomorph/xenomorph/reserved.rkt
+++ b/xenomorph/xenomorph/reserved.rkt
@@ -8,7 +8,7 @@ https://github.com/mbutterick/restructure/blob/master/src/Reserved.coffee
 |#
 
 (define x:reserved%
-  (class xenobase%
+  (class x:base%
     (super-new)
     (init-field [(@type type)] [(@count count)])
 
diff --git a/xenomorph/xenomorph/string.rkt b/xenomorph/xenomorph/string.rkt
index 23f68d5e..cafccc6c 100644
--- a/xenomorph/xenomorph/string.rkt
+++ b/xenomorph/xenomorph/string.rkt
@@ -29,7 +29,7 @@ https://github.com/mbutterick/restructure/blob/master/src/String.coffee
   (not (eof-object? (peek-byte port))))
 
 (define x:string%
-  (class xenobase%
+  (class x:base%
     (super-new)
     (init-field [(@len len)] [(@encoding encoding)])
 
diff --git a/xenomorph/xenomorph/struct.rkt b/xenomorph/xenomorph/struct.rkt
index 1a695d0f..6120943d 100644
--- a/xenomorph/xenomorph/struct.rkt
+++ b/xenomorph/xenomorph/struct.rkt
@@ -44,7 +44,7 @@ https://github.com/mbutterick/restructure/blob/master/src/Struct.coffee
   h)
 
 (define x:struct%
-  (class xenobase%
+  (class x:base%
     (super-new)
     (init-field [(@fields fields)])