diff --git a/syndicate/mc/preserve.rkt b/syndicate/mc/preserve.rkt
index 01d52d7..fed3b51 100644
--- a/syndicate/mc/preserve.rkt
+++ b/syndicate/mc/preserve.rkt
@@ -284,10 +284,7 @@
   (define (skip-whitespace) (skip-whitespace* i))
 
   (define (read-sequence terminator)
-    (sequence-fold '() accumulate-value reverse terminator))
-
-  (define (accumulate-value acc)
-    (cons (read-value) acc))
+    (sequence-fold '() (lambda (acc) (cons (read-value) acc)) reverse terminator))
 
   (define (read-dictionary-or-set)
     (sequence-fold #f
@@ -301,7 +298,7 @@
                             (hash-set (or acc (hash)) k v)]
                        [_ (when (hash? acc) (parse-error "Missing expected key/value separator"))
                           (set-add (or acc (set)) k)]))
-                   values
+                   (lambda (acc) (or acc (hash)))
                    #\}))
 
   (define PIPE #\|)
@@ -471,7 +468,7 @@
        [(== PIPE) (read-char i) (string->symbol (read-string PIPE))]
        [#\# (match i
               [(px #px#"^#set\\{" (list _))
-               (sequence-fold (set) accumulate-value values #\})]
+               (sequence-fold (set) (lambda (acc) (set-add acc (read-value))) values #\})]
               [(px #px#"^#hexvalue\\{" (list _))
                (decode (read-hex-binary '()) (lambda () (parse-error "Invalid #hexvalue encoding")))]
               [(px #px#"^#true" (list _))
@@ -633,6 +630,15 @@
   (cross-check "#base64{SGk}" #"Hi" (#x62 "Hi"))
   (cross-check "#base64{ S G k }" #"Hi" (#x62 "Hi"))
 
+  (check-equal? (string->preserve "[]") '())
+  (check-equal? (string->preserve "{}") (hash))
+  (check-equal? (string->preserve "\"\"") "")
+  (check-equal? (string->preserve "||") (string->symbol ""))
+  (check-equal? (string->preserve "#set{}") (set))
+
+  (check-equal? (string->preserve "{1 2 3}") (set 1 2 3))
+  (check-equal? (string->preserve "#set{1 2 3}") (set 1 2 3))
+
   (cross-check "\"abc\\u6c34\\u6C34\\\\\\/\\\"\\b\\f\\n\\r\\txyz\""
                "abc\u6c34\u6c34\\/\"\b\f\n\r\txyz"
                (#x5f #x14