diff --git a/xenomorph/xenomorph/util.rkt b/xenomorph/xenomorph/util.rkt
index 79690330..31c987bb 100644
--- a/xenomorph/xenomorph/util.rkt
+++ b/xenomorph/xenomorph/util.rkt
@@ -12,4 +12,7 @@
     [(? procedure? proc) (proc parent)]
     [(? symbol? key) #:when parent (dict-ref parent key)]
     [(? x:int?) #:when port (decode x port)]
-    [_ (raise-argument-error 'resolve-length "fixed-size argument" x)]))
\ No newline at end of file
+    [_ (raise-argument-error 'resolve-length "fixed-size argument" x)]))
+
+
+(struct PropertyDescriptor (kvs) #:transparent)