diff --git a/pungi/phases/livemedia_phase.py b/pungi/phases/livemedia_phase.py
index fe8720f2..1125a1e9 100644
--- a/pungi/phases/livemedia_phase.py
+++ b/pungi/phases/livemedia_phase.py
@@ -122,6 +122,12 @@ class LiveMediaThread(WorkerThread):
                                % (output['task_id'], log_file))
         return output
 
+    def _get_cmd(self, koji_wrapper, config):
+        """Replace `arches` (as list) with `arch` as a comma-separated string."""
+        copy = dict(config)
+        copy['arch'] = ','.join(copy.pop('arches', []))
+        return koji_wrapper.get_live_media_cmd(copy)
+
     def worker(self, compose, variant, config):
         msg = 'Live media: %s (arches: %s, variant: %s)' % (config['name'],
                                                             ' '.join(config['arches']),
@@ -129,7 +135,7 @@ class LiveMediaThread(WorkerThread):
         self.pool.log_info('[BEGIN] %s' % msg)
 
         koji_wrapper = KojiWrapper(compose.conf['koji_profile'])
-        cmd = koji_wrapper.get_live_media_cmd(config)
+        cmd = self._get_cmd(koji_wrapper, config)
 
         log_file = self._get_log_file(compose, variant, config)
         output = self._run_command(koji_wrapper, cmd, compose, log_file)
diff --git a/tests/test_livemediaphase.py b/tests/test_livemediaphase.py
index 4b2d2b34..b72ee5ee 100755
--- a/tests/test_livemediaphase.py
+++ b/tests/test_livemediaphase.py
@@ -222,7 +222,18 @@ class TestCreateImageBuildThread(unittest.TestCase):
         self.assertEqual(run_blocking_cmd.mock_calls,
                          [mock.call('koji-spin-livemedia', log_file='/a/b/log/log_file')])
         self.assertEqual(get_live_media_cmd.mock_calls,
-                         [mock.call(config)])
+                         [mock.call({'arch': 'amd64,x86_64',
+                                     'kickstart': 'file.ks',
+                                     'ksurl': 'git://example.com/repo.git',
+                                     'ksversion': None,
+                                     'name': 'Fedora Server Live',
+                                     'release': None,
+                                     'repo': ['/repo/$arch/Server'],
+                                     'scratch': False,
+                                     'skip_tag': None,
+                                     'target': 'f24',
+                                     'title': None,
+                                     'version': 'Rawhide'})])
         self.assertEqual(get_image_paths.mock_calls,
                          [mock.call(1234)])
         self.assertItemsEqual(makedirs.mock_calls,