diff --git a/implementations/racket/preserves/main.rkt b/implementations/racket/preserves/main.rkt
index bdaa1c2..720cd17 100644
--- a/implementations/racket/preserves/main.rkt
+++ b/implementations/racket/preserves/main.rkt
@@ -289,8 +289,9 @@
                      (define k (read-value))
                      (skip-whitespace)
                      (match (peek-char i)
-                       [#\: (when (set? acc) (parse-error "Unexpected key/value separator in set"))
-                            (read-char i)
+                       [#\: (read-char i)
+                            (when (set? acc)
+                              (parse-error "Unexpected key/value separator in set"))
                             (define v (read-value))
                             (hash-set (or acc (hash)) k v)]
                        [_ (when (hash? acc) (parse-error "Missing expected key/value separator"))
@@ -306,7 +307,9 @@
            (? char? (or #\( #\) #\{ #\} #\[ #\]
                         #\" #\; #\, #\# #\: (== PIPE)
                         (? char-whitespace?))))
-       (string->symbol (list->string (reverse acc)))]
+       (if (null? acc)
+           (parse-error "Invalid character ~v at start of value; skipping" (read-char i))
+           (string->symbol (list->string (reverse acc))))]
       [_ (read-raw-symbol (cons (read-char i) acc))]))
 
   (define (read-base64-binary acc)
@@ -484,7 +487,7 @@
                (read-base64-binary '())]
               [_
                (parse-error "Invalid preserve value")])]
-       [#\: (parse-error "Unexpected key/value separator between items")]
+       [#\: (read-char i) (parse-error "Unexpected key/value separator between items")]
        [_ (read-raw-symbol '())])))
 
   (read-value))