--- a/testing/taskcluster/mach_commands.py
+++ b/testing/taskcluster/mach_commands.py
@@ -332,17 +332,17 @@ class Graph(object):
         changed_files = set()
         if vcs_info:
             pushdate = time.strftime('%Y%m%d%H%M%S', time.gmtime(vcs_info.pushdate))
 
             sys.stderr.write('%d commits influencing task scheduling:\n' %
                              len(vcs_info.changesets))
             for c in vcs_info.changesets:
                 sys.stderr.write('%s %s\n' % (
-                    c['node'][0:12], c['desc'].splitlines()[0]))
+                    c['node'][0:12], c['desc'].splitlines()[0].encode('ascii', 'ignore')))
 
                 changed_files |= set(c['files'])
 
         # Template parameters used when expanding the graph
         seen_images = {}
         parameters = dict(gaia_info().items() + {
             'index': 'index',
             'project': project,