diff --git a/file/sniffer.js b/file/sniffer.js
index adb2c52..d14a68a 100644
--- a/file/sniffer.js
+++ b/file/sniffer.js
@@ -6,11 +6,6 @@
  * Copyright(c) 2020 Google Inc.
  */
 
-var bitjs = bitjs || {};
-bitjs.file = bitjs.file || {};
-
-(function() {
-
 // A selection from https://en.wikipedia.org/wiki/List_of_file_signatures.
 // Mapping of MIME type to magic numbers.  Each file type can have multiple signatures.
 // '??' is used as a placeholder value.
@@ -79,7 +74,7 @@ for (const mimeType in fileSignatures) {
  * @param {ArrayBuffer} ab
  * @return {string} The MIME type of the buffer, or undefined.
  */
-bitjs.file.findMimeType = function(ab) {
+export function findMimeType(ab) {
   const depth = ab.byteLength < maxDepth ? ab.byteLength : maxDepth;
   const arr = new Uint8Array(ab).subarray(0, depth);
   let curNode = root;
@@ -94,5 +89,3 @@ bitjs.file.findMimeType = function(ab) {
     if (curNode.mimeType) return curNode.mimeType;
   }
 };
-
-})();
diff --git a/tests/file-sniffer-test.html b/tests/file-sniffer-test.html
index d4a1ead..f6a3dc4 100644
--- a/tests/file-sniffer-test.html
+++ b/tests/file-sniffer-test.html
@@ -3,10 +3,11 @@
 <head>
     <title>Unit tests for bitjs.io.ByteStreamBitStream</title>
     <script src="muther.js"></script>
-    <script src="../file/sniffer.js"></script>
 </head>
 <body>
-<script>
+<script type="module">
+  import { findMimeType } from '../file/sniffer.js';
+
   const assert = muther.assert;
   const assertEquals = muther.assertEquals;
   const assertThrows = muther.assertThrows;
@@ -14,7 +15,7 @@
   function sniffTest(mimeType, sig) {
     const array = new Uint8Array(16);
     array.set(sig);
-    assertEquals(mimeType, bitjs.file.findMimeType(array.buffer));
+    assertEquals(mimeType, findMimeType(array.buffer));
   }
 
   muther.go({
