diff --git a/src/allmydata/storage/immutable.py b/src/allmydata/storage/immutable.py
index 8d83ec1b3..778c0ddf8 100644
--- a/src/allmydata/storage/immutable.py
+++ b/src/allmydata/storage/immutable.py
@@ -1,4 +1,15 @@
-from future.utils import bytes_to_native_str
+"""
+Ported to Python 3.
+"""
+
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+from __future__ import unicode_literals
+
+from future.utils import PY2, bytes_to_native_str
+if PY2:
+    from future.builtins import filter, map, zip, ascii, chr, hex, input, next, oct, open, pow, round, super, bytes, dict, list, object, range, str, max, min  # noqa: F401
 
 import os, stat, struct, time
 
diff --git a/src/allmydata/util/_python3.py b/src/allmydata/util/_python3.py
index afdbea1f0..5a26d2cbc 100644
--- a/src/allmydata/util/_python3.py
+++ b/src/allmydata/util/_python3.py
@@ -37,6 +37,7 @@ PORTED_MODULES = [
     "allmydata.monitor",
     "allmydata.storage.crawler",
     "allmydata.storage.expirer",
+    "allmydata.storage.immutable",
     "allmydata.test.common_py3",
     "allmydata.uri",
     "allmydata.util._python3",