diff --git a/ssh-message-types.rkt b/ssh-message-types.rkt
index ff67532..5c8e58a 100644
--- a/ssh-message-types.rkt
+++ b/ssh-message-types.rkt
@@ -14,6 +14,8 @@
 (provide ssh-message-decode
 	 ssh-message-encode)
 
+(provide (struct-out ssh-msg-kexinit))
+
 (define decoder-map (make-hasheqv))
 
 (define-values (prop:ssh-message-encoder ssh-message-encoder? ssh-message-encoder)
@@ -29,13 +31,12 @@
      packet)))
 
 (define (ssh-message-encode m)
-  ((ssh-message-encoder m) m))
+  (bit-string->bytes ((ssh-message-encoder m) m)))
 
 (define-syntax define-ssh-message-type
   (syntax-rules ()
     ((_ name type-byte-value (field-type field-name) ...)
      (begin
-       (provide (struct-out name))
        (struct name (field-name ...)
 	       #:transparent
 	       #:property prop:ssh-message-encoder
@@ -95,16 +96,16 @@
 	 (boolean
 	  #`(#,temp-name))
 	 (uint32
-	  #`((#,temp-name :: integer bits 32)))
+	  #`((#,temp-name :: unsigned integer bits 32)))
 	 (uint64
-	  #`((#,temp-name :: integer bits 64)))
+	  #`((#,temp-name :: unsigned integer bits 64)))
 	 (string
 	  (let ((length-name (car (generate-temporaries (list temp-name)))))
 	    #`((#,length-name :: integer bits 32)
 	       (#,temp-name :: binary bytes #,length-name))))
 	 (mpint
 	  (let ((length-name (car (generate-temporaries (list temp-name)))))
-	    #`((#,@length-name :: integer bits 32)
+	    #`((#,length-name :: integer bits 32)
 	       (#,temp-name :: binary bytes #,length-name))))
 	 (name-list
 	  (let ((length-name (car (generate-temporaries (list temp-name)))))
@@ -115,7 +116,9 @@
 	((byte n) #`(bit-string->bytes #,temp-name))
 	(boolean #`(not (zero? #,temp-name)))
 	(string #`(bit-string->bytes #,temp-name))
-	(mpint #`(bit-string->integer #,temp-name))
+	(mpint #`(if (zero? (bit-string-length #,temp-name))
+		     0
+		     (bit-string->integer #,temp-name #t #t)))
 	(name-list #`(name-list->symbols #,temp-name))
 	(else temp-name)))
     (syntax-case stx ()
@@ -124,8 +127,8 @@
 	      (temp-names (generate-temporaries field-types)))
 	 #`(lambda (packet)
 	     (bit-string-case packet
-	       (( type-byte-value
-		  #,@(append* (map field-extractor temp-names field-types)))
+	       (( (= type-byte-value)
+		  #,@(append* (map field-extractor temp-names field-types)) )
 		(struct-name #,@(map field-transformer temp-names field-types))))))))))
 
 (define (mpint-width n)
@@ -152,6 +155,31 @@
       '()
       (map string->symbol (regexp-split #rx"," (bytes->string/utf-8 (bit-string->bytes bs))))))
 
+(struct test-message (value)
+	#:transparent
+	#:property prop:ssh-message-encoder (compute-ssh-message-encoder 123 mpint))
+(let ((test-decode (compute-ssh-message-decoder test-message 123 mpint)))
+  (define (bidi-check msg enc-without-type-tag)
+    (let ((enc (bytes-append (bytes 123) enc-without-type-tag)))
+      (let ((msg-enc (ssh-message-encode msg))
+	    (enc-msg (test-decode enc)))
+	(if (and (equal? msg-enc enc)
+		 (equal? enc-msg msg))
+	    'ok
+	    `(fail ,msg-enc ,enc-msg)))))
+  (check-eqv? (bidi-check (test-message 0) (bytes 0 0 0 0)) 'ok)
+  (check-eqv? (bidi-check (test-message #x9a378f9b2e332a7)
+			  (bytes #x00 #x00 #x00 #x08
+				 #x09 #xa3 #x78 #xf9
+				 #xb2 #xe3 #x32 #xa7)) 'ok)
+  (check-eqv? (bidi-check (test-message #x80)
+			  (bytes #x00 #x00 #x00 #x02 #x00 #x80)) 'ok)
+  (check-eqv? (bidi-check (test-message #x-1234)
+			  (bytes #x00 #x00 #x00 #x02 #xed #xcc)) 'ok)
+  (check-eqv? (bidi-check (test-message #x-deadbeef)
+			  (bytes #x00 #x00 #x00 #x05
+				 #xff #x21 #x52 #x41 #x11)) 'ok))
+
 (define-ssh-message-type ssh-msg-kexinit SSH_MSG_KEXINIT
      ((byte 16)    cookie)
      (name-list    kex_algorithms)