diff --git a/python/mozbuild/mozbuild/jar.py b/python/mozbuild/mozbuild/jar.py
index 0aa7c3d7d512..62ae2a9bca92 100644
--- a/python/mozbuild/mozbuild/jar.py
+++ b/python/mozbuild/mozbuild/jar.py
@@ -14,6 +14,7 @@ import sys
 import os
 import errno
 import re
+import six
 import logging
 from time import localtime
 from MozZipFile import ZipFile
@@ -306,7 +307,7 @@ class JarMaker(object):
         '''
         myregister = dict.fromkeys(map(lambda s: s.replace('%',
                                                            chromebasepath), register))
-        addEntriesToListFile(manifestPath, myregister.iterkeys())
+        addEntriesToListFile(manifestPath, six.iterkeys(myregister))
 
     def makeJar(self, infile, jardir):
         '''makeJar is the main entry point to JarMaker.
diff --git a/python/mozbuild/mozpack/test/test_packager_formats.py b/python/mozbuild/mozpack/test/test_packager_formats.py
index a7b0afbf9c53..665d348a5abc 100644
--- a/python/mozbuild/mozpack/test/test_packager_formats.py
+++ b/python/mozbuild/mozpack/test/test_packager_formats.py
@@ -234,7 +234,7 @@ RESULT_OMNIJAR.update({
             'components/foo.js',
         ), (
             mozpath.relpath(p, 'app')
-            for p in RESULT_FLAT.iterkeys()
+            for p in six.iterkeys(RESULT_FLAT)
             if p.startswith('app/chrome/addons/addon2/')
         ))
     },