diff --git a/scheme/lib/ftp.scm b/scheme/lib/ftp.scm
index 11f0475..b2775d7 100644
--- a/scheme/lib/ftp.scm
+++ b/scheme/lib/ftp.scm
@@ -392,22 +392,12 @@
 (define (ftp-build-PORT-string sockaddr)
   (let* ((hst-info (host-info (system-name)))
          (ip-address (car (host-info:addresses hst-info))))
-  (receive (hst-address srvc-port)
-      (socket-address->internet-address sockaddr)
-    (let* ((num32 ip-address)
-	   (num24 (arithmetic-shift num32 -8))
-	   (num16 (arithmetic-shift num24 -8))
-	   (num08 (arithmetic-shift num16 -8))
-	   (byte0 (bitwise-and #b11111111 num08))
-	   (byte1 (bitwise-and #b11111111 num16))
-	   (byte2 (bitwise-and #b11111111 num24))
-	   (byte3 (bitwise-and #b11111111 num32)))
-      (format #f "PORT ~a,~a,~a,~a,~a,~a"
-	      byte0 byte1 byte2 byte3
-	      (arithmetic-shift srvc-port -8) ; high order byte
-	      (bitwise-and #b11111111 srvc-port) ; lower order byte
-	      )))))
-  
+    (receive (hst-address srvc-port)
+	(socket-address->internet-address sockaddr)
+      (string-append "PORT "
+		     (format-internet-host-address ip-address ",")
+		     ","
+		     (format-port srvc-port)))))
 
 (define (ftp-send-command connection command . maybe-expected)
   (let-optionals* maybe-expected ((expected "2.."))
diff --git a/scheme/packages.scm b/scheme/packages.scm
index a649e3e..11a90af 100644
--- a/scheme/packages.scm
+++ b/scheme/packages.scm
@@ -412,6 +412,7 @@
 	(subset srfi-13 (string-join))
 	let-opt
 	sunet-utilities
+	format-net
 	crlf-io)
   (files (lib ftp)))