diff --git a/src/allmydata/encode.py b/src/allmydata/encode.py
index f22e72cc6..50c3c389b 100644
--- a/src/allmydata/encode.py
+++ b/src/allmydata/encode.py
@@ -3,7 +3,7 @@
 from zope.interface import implements
 from twisted.internet import defer
 from twisted.python import log
-from allmydata.hashtree import HashTree, roundup_pow2
+from allmydata.hashtree import HashTree
 from allmydata.Crypto.Cipher import AES
 from allmydata.util import mathutil, hashutil
 from allmydata.util.assertutil import _assert