diff --git a/IPython/html/tests/test_files.py b/IPython/html/tests/test_files.py
index e3dc1ec..82c630d 100644
--- a/IPython/html/tests/test_files.py
+++ b/IPython/html/tests/test_files.py
@@ -91,7 +91,8 @@ class FilesTest(NotebookTestBase):
         r = requests.get(url_path_join(base, 'files', 'test.bin'))
         self.assertEqual(r.status_code, 200)
         self.assertEqual(r.headers['content-type'], 'application/octet-stream')
-        self.assertTrue(r.content[0] == 255 or r.content[0] == b'\xff')
+        # self.assertTrue(r.content[0] == 255 or r.content[0] == b'\xff')
+        self.assertEqual(r.content[:1], b'\xff')
         self.assertEqual(len(r.content), 6)
 
         r = requests.get(url_path_join(base, 'files', 'test.txt'))