diff --git a/syndicate/actor.rkt b/syndicate/actor.rkt
index 96577f4..ddfb41a 100644
--- a/syndicate/actor.rkt
+++ b/syndicate/actor.rkt
@@ -7,7 +7,7 @@
 
          (struct-out entity-ref)
          attenuate-entity-ref
-         parse-Ref
+         parse-Ref!
          Ref->preserves
 
          actor-system
@@ -80,7 +80,7 @@
    #:sync [entity-sync #f]))
 
 (struct entity-ref (relay target attenuation) #:transparent)
-(define (parse-Ref r) (if (entity-ref? r) r eof))
+(define (parse-Ref! r) (if (entity-ref? r) r (error 'parse-Ref! "Expected entity-ref; got ~v" r)))
 (define (Ref->preserves r) r)
 
 (struct outbound-assertion (handle peer [established? #:mutable]))