--- a/mozilla-tests/thunderbird_config.py
+++ b/mozilla-tests/thunderbird_config.py
@@ -449,16 +449,17 @@ for platform in PLATFORMS.keys():
 for _, branch in items_at_least(BRANCHES, 'gecko_version', 30):
     branch['script_repo_manifest'] = \
         "https://hg.mozilla.org/%(moz_repo_path)s/raw-file/default/" + \
         "testing/mozharness/mozharness.json"
     # mozharness_archiver_repo_path tells the factory to use a copy of mozharness from within the
     #  gecko tree and also allows us to overwrite which gecko repo to use. Useful for platforms
     # like Thunderbird
     branch['mozharness_archiver_repo_path'] = '%(moz_repo_path)s'
+    branch['mozharness_archiver_rev'] = 'default'
 
 if __name__ == "__main__":
     import sys
     import pprint
 
     args = sys.argv[1:]
 
     if len(args) > 0:

--- a/mozilla/thunderbird_config.py
+++ b/mozilla/thunderbird_config.py
@@ -1063,16 +1063,17 @@ for branch in branches:
 for _, branch in items_at_least(BRANCHES, 'gecko_version', 30):
     branch['script_repo_manifest'] = \
         "https://hg.mozilla.org/%(moz_repo_path)s/raw-file/default/" + \
         "testing/mozharness/mozharness.json"
     # mozharness_archiver_repo_path tells the factory to use a copy of mozharness from within the
     #  gecko tree and also allows us to overwrite which gecko repo to use. Useful for platforms
     # like Thunderbird
     branch['mozharness_archiver_repo_path'] = '%(moz_repo_path)s'
+    branch['mozharness_archiver_rev'] = 'default'
 
 if __name__ == "__main__":
     import sys
     import pprint
     args = sys.argv[1:]
 
     if len(args) > 0:
         items = dict([(b, BRANCHES[b]) for b in args])