diff --git a/websockets.scm b/websockets.scm
index c4a761b..a8eed6d 100644
--- a/websockets.scm
+++ b/websockets.scm
@@ -23,10 +23,17 @@
    ;; fragment-optype
    )
 
-(import chicken scheme data-structures extras ports posix foreign
-        srfi-13 srfi-14 srfi-18)
-(use srfi-1 srfi-4 spiffy intarweb uri-common base64 simple-sha1
-     mailbox comparse)
+(cond-expand
+  (chicken-4
+    (import chicken scheme data-structures extras ports posix foreign
+            srfi-13 srfi-14 srfi-18)
+    (use srfi-1 srfi-4 spiffy intarweb uri-common base64 simple-sha1
+         mailbox comparse))
+  (chicken-5
+    (import scheme srfi-4 srfi-8 srfi-13 srfi-14 srfi-18 base64 comparse
+            intarweb mailbox simple-sha1 spiffy (chicken base) (chicken blob)
+            (chicken bitwise) (chicken condition) (chicken foreign)
+            (chicken io))))
 
 (define-inline (neq? obj1 obj2) (not (eq? obj1 obj2)))
 
@@ -248,12 +255,12 @@
                      (bl1 (read-byte inbound-port)))
                  (set! frame-payload-length (+ (arithmetic-shift bl0 8) bl1))))
               ((= frame-payload-length 127)
-               (define (shift i r)
-                 (if (< i 0)
-                     r
-                     (shift (- i 1) (+ (arithmetic-shift (read-byte inbound-port) (* 8 i))
-                                       r))))
-               (set! frame-payload-length (shift 7 0))))
+               (letrec ((shift (lambda (i r)
+                                 (if (< i 0)
+                                     r
+                                     (shift (- i 1) (+ (arithmetic-shift (read-byte inbound-port) (* 8 i))
+                                                       r))))))
+               (set! frame-payload-length (shift 7 0)))))
         (when (or (> frame-payload-length (max-frame-size))
                   (> (+ frame-payload-length total-size) (max-message-size)))
               (signal (make-websocket-exception