diff --git a/scheme/cyclone/util.sld b/scheme/cyclone/util.sld
index f43cf1df..eb0ceb14 100644
--- a/scheme/cyclone/util.sld
+++ b/scheme/cyclone/util.sld
@@ -2,6 +2,7 @@
   (import (scheme base)
           (scheme char))
   (export
+    filter
     tagged-list?
     mangle
     mangle-global)
diff --git a/transforms.scm b/transforms.scm
index be164230..b414daab 100644
--- a/transforms.scm
+++ b/transforms.scm
@@ -273,19 +273,6 @@
       env
       (assq-remove-keys (assq-remove-key env (car keys)) (cdr keys))))
 
-;; Simplified version of filter from SRFI 1
-(define (filter pred lis)
-  (let recur ((lis lis))
-   (if (null? lis)
-    lis
-    (let ((head (car lis))
-          (tail (cdr lis)))
-      (if (pred head)
-          (let ((new-tail (recur tail)))
-        (if (eq? tail new-tail) lis
-            (cons head new-tail)))
-          (recur tail))))))
-
 
 ;; Data type predicates and accessors.
 
diff --git a/util.scm b/util.scm
index 54bcd01a..102697c6 100644
--- a/util.scm
+++ b/util.scm
@@ -1,3 +1,10 @@
+;;
+;; Cyclone Scheme
+;; Copyright (c) 2015, Justin Ethier
+;; All rights reserved.
+;;
+;; This module contains various utility functions.
+;;
 
 (define (tagged-list? tag exp)
   (if (pair? exp)
@@ -15,6 +22,21 @@
 (define (integer->char-list n)
   (string->list (number->string n)))
 
+;; Simplified version of filter from SRFI 1
+(define (filter pred lis)
+  (letrec ((recur (lambda (lis)
+                    (if (null? lis)
+                     lis
+                     (let ((head (car lis))
+                           (tail (cdr lis)))
+                       (if (pred head)
+                           (let ((new-tail (recur tail)))
+                         (if (eq? tail new-tail) lis
+                             (cons head new-tail)))
+                           (recur tail)))))))
+    (recur lis)))
+
+
 ;; Name-mangling.
 
 ;; We have to "mangle" Scheme identifiers into