diff --git a/pungi/wrappers/kojiwrapper.py b/pungi/wrappers/kojiwrapper.py
index 850e964c..033d29e6 100644
--- a/pungi/wrappers/kojiwrapper.py
+++ b/pungi/wrappers/kojiwrapper.py
@@ -23,6 +23,7 @@ import contextlib
 
 import koji
 from kobo.shortcuts import run
+import six
 from six.moves import configparser
 
 from .. import util
@@ -171,6 +172,9 @@ class KojiWrapper(object):
         for section, opts in config_options.items():
             cfg_parser.add_section(section)
             for option, value in opts.items():
+                if not isinstance(value, six.string_types):
+                    # Python 3 configparser will reject non-string values.
+                    value = str(value)
                 cfg_parser.set(section, option, value)
 
         fd = open(conf_file_dest, "w")
diff --git a/tests/test_koji_wrapper.py b/tests/test_koji_wrapper.py
index 16a70ac2..1a10c9d7 100644
--- a/tests/test_koji_wrapper.py
+++ b/tests/test_koji_wrapper.py
@@ -83,6 +83,7 @@ class KojiWrapperTest(KojiWrapperBaseTestCase):
                     'ksurl': 'git://example.com/ks.git',
                     'distro': 'test-distro',
                     'release': '20160222.0',
+                    'disk_size': 4,
                 }
             },
             self.tmpfile
@@ -105,7 +106,8 @@ class KojiWrapperTest(KojiWrapperBaseTestCase):
                                'kickstart = test-kickstart',
                                'ksurl = git://example.com/ks.git',
                                'distro = test-distro',
-                               'release = 20160222.0'])
+                               'release = 20160222.0',
+                               'disk_size = 4'])
 
     def test_get_image_paths(self):