diff --git a/syndicate/mc/preserve.rkt b/syndicate/mc/preserve.rkt
index 1ccd553..d0f08e8 100644
--- a/syndicate/mc/preserve.rkt
+++ b/syndicate/mc/preserve.rkt
@@ -315,34 +315,36 @@
        (string->symbol (list->string (reverse acc)))]
       [_ (read-raw-symbol (cons (read-char i) acc))]))
 
-  (define (read-encoded-binary kind valid-char? finish)
-    (let loop ((acc '()))
-      (skip-whitespace)
-      (let ((ch (read/no-eof)))
-        (cond [(valid-char? ch)
-               (loop (cons ch acc))]
-              [(eqv? ch #\})
-               (finish (list->string (reverse acc)))]
-              [else (parse-error "Invalid ~a character" kind)]))))
+  (define (read-base64-binary acc)
+    (skip-whitespace)
+    (define ch (read/no-eof))
+    (cond [(eqv? ch #\})
+           (base64-decode (string->bytes/latin-1 (list->string (reverse acc))))]
+          [(or (and (char>=? ch #\A) (char<=? ch #\Z))
+               (and (char>=? ch #\a) (char<=? ch #\z))
+               (and (char>=? ch #\0) (char<=? ch #\9))
+               (memv ch '(#\+ #\/ #\- #\_ #\=)))
+           (read-base64-binary (cons ch acc))]
+          [else
+           (parse-error "Invalid base64 character")]))
 
-  (define (read-base64-binary)
-    (read-encoded-binary "base64"
-                         (lambda (ch)
-                           (or (and (char>=? ch #\A) (char<=? ch #\Z))
-                               (and (char>=? ch #\a) (char<=? ch #\z))
-                               (and (char>=? ch #\0) (char<=? ch #\9))
-                               (memv ch '(#\+ #\/ #\- #\_ #\=))))
-                         (lambda (s)
-                           (base64-decode (string->bytes/latin-1 s)))))
+  (define (hexdigit? ch)
+    (or (and (char>=? ch #\A) (char<=? ch #\F))
+        (and (char>=? ch #\a) (char<=? ch #\f))
+        (and (char>=? ch #\0) (char<=? ch #\9))))
 
-  (define (read-hex-binary)
-    (read-encoded-binary "hex"
-                         (lambda (ch)
-                           (or (and (char>=? ch #\A) (char<=? ch #\F))
-                               (and (char>=? ch #\a) (char<=? ch #\f))
-                               (and (char>=? ch #\0) (char<=? ch #\9))))
-                         (lambda (s)
-                           (hex-string->bytes s))))
+  (define (read-hex-binary acc)
+    (skip-whitespace)
+    (define ch (read/no-eof))
+    (cond [(eqv? ch #\})
+           (hex-string->bytes (list->string (reverse acc)))]
+          [(hexdigit? ch)
+           (define ch2 (read/no-eof))
+           (when (not (hexdigit? ch2))
+             (parse-error "Hex-encoded binary digits must come in pairs"))
+           (read-hex-binary (cons ch2 (cons ch acc)))]
+          [else
+           (parse-error "Invalid hex character")]))
 
   (define (read-stringlike xform-item finish terminator-char hexescape-char hexescape-proc)
     (let loop ((acc '()))
@@ -368,11 +370,11 @@
                        (integer->char
                         (match i
                           [(px #px#"^[a-fA-F0-9]{4}" (list hexdigits))
-                           (define n1 (string->number (bytes->string/utf-8 hexdigits)))
+                           (define n1 (string->number (bytes->string/utf-8 hexdigits) 16))
                            (if (<= #xd800 n1 #xdfff) ;; surrogate pair first half
                                (match i
                                  [(px #px#"^\\\\u([a-fA-F0-9]{4})" (list hexdigits2))
-                                  (define n2 (string->number (bytes->string/utf-8 hexdigits2)))
+                                  (define n2 (string->number (bytes->string/utf-8 hexdigits2) 16))
                                   (if (<= #xdc00 n2 #xdfff)
                                       (+ (arithmetic-shift (- n1 #xd800) 10)
                                          (- n2 #xdc00)
@@ -472,7 +474,7 @@
               [(px #px#"^#set\\{" (list _))
                (sequence-fold (set) accumulate-value values #\})]
               [(px #px#"^#hexvalue\\{" (list _))
-               (decode (read-hex-binary) (lambda () (parse-error "Invalid #hexvalue encoding")))]
+               (decode (read-hex-binary '()) (lambda () (parse-error "Invalid #hexvalue encoding")))]
               [(px #px#"^#true" (list _))
                #t]
               [(px #px#"^#false" (list _))
@@ -480,9 +482,9 @@
               [(px #px#"^#\"" (list _))
                (read-literal-binary)]
               [(px #px#"^#hex\\{" (list _))
-               (read-hex-binary)]
+               (read-hex-binary '())]
               [(px #px#"^#base64\\{" (list _))
-               (read-base64-binary)]
+               (read-base64-binary '())]
               [_
                (parse-error "Invalid preserve value")])]
        [#\: (parse-error "Unexpected key/value separator between items")]
@@ -570,7 +572,7 @@
        #'(let ((val v)) (cross-check text v v (b ...))))
       ((_ text forward back (b ...))
        #`(let ((loc #,(source-location->string #'forward)))
-           (check-equal? (string->preserve text) back)
+           (check-equal? (string->preserve text) back loc)
            (check-equal? (d (encode forward)) back loc)
            (check-equal? (d (encode back)) back loc)
            (check-equal? (d (expected b ...)) back loc)
@@ -583,7 +585,7 @@
        #'(let ((val v)) (cross-check/nondeterministic text v v (b ...))))
       ((_ text forward back (b ...))
        #`(let ((loc #,(source-location->string #'forward)))
-           (check-equal? (string->preserve text) back)
+           (check-equal? (string->preserve text) back loc)
            (check-equal? (d (encode forward)) back loc)
            (check-equal? (d (encode back)) back loc)
            (check-equal? (d (expected b ...)) back loc)
@@ -620,6 +622,25 @@
                `("hello" there #"world" () ,(set) #t #f)
                (#xC7 #x55 "hello" #x75 "there" #x65 "world" #xC0 #xD0 #x01 #x00))
 
+  (cross-check "#\"ABC\"" #"ABC" (#x63 #x41 #x42 #x43))
+  (cross-check "#hex{414243}" #"ABC" (#x63 #x41 #x42 #x43))
+  (cross-check "#hex{ 41 4A 4e }" #"AJN" (#x63 #x41 #x4A #x4E))
+  (cross-check "#hex{ 41;re\n 42 43 }" #"ABC" (#x63 #x41 #x42 #x43))
+  (check-exn exn? (lambda () (string->preserve "#hex{414 243}"))) ;; bytes must be 2-digits entire
+  (cross-check "#base64{Y29yeW1i}" #"corymb" (#x66 "corymb"))
+  (cross-check "#base64{Y29 yeW 1i}" #"corymb" (#x66 "corymb"))
+  (cross-check ";; a comment\n#base64{\n;x\nY29 yeW 1i}" #"corymb" (#x66 "corymb"))
+  (cross-check "#base64{SGk=}" #"Hi" (#x62 "Hi"))
+  (cross-check "#base64{SGk}" #"Hi" (#x62 "Hi"))
+  (cross-check "#base64{ S G k }" #"Hi" (#x62 "Hi"))
+
+  (cross-check "\"abc\\u6c34\\u6C34\\\\\\/\\\"\\b\\f\\n\\r\\txyz\""
+               "abc\u6c34\u6c34\\/\"\b\f\n\r\txyz"
+               (#x5f #x14
+                     #x61 #x62 #x63 #xe6 #xb0 #xb4 #xe6 #xb0
+                     #xb4 #x5c #x2f #x22 #x08 #x0c #x0a #x0d
+                     #x09 #x78 #x79 #x7a))
+
   (cross-check "-257" -257 (#x42 #xFE #xFF))
   (cross-check "-256" -256 (#x42 #xFF #x00))
   (cross-check "-255" -255 (#x42 #xFF #x01))