--- a/python/mozbuild/mozbuild/action/langpack_manifest.py
+++ b/python/mozbuild/mozbuild/action/langpack_manifest.py
@@ -46,16 +46,19 @@ pushlog_api_url = "{0}/json-rev/{1}"
 #    (datetime) - a datetime object
 #
 # Example:
 #    dt = get_dt_from_hg("/var/vcs/l10n-central/pl")
 #    dt == datetime(2017, 10, 11, 23, 31, 54, 0)
 ###
 def get_dt_from_hg(path):
     with mozversioncontrol.get_repository_object(path=path) as repo:
+        phase = repo._run_in_client(["log", "-r", ".", "-T" "{phase}"])
+        if phase.strip() != "public":
+            return datetime.datetime.utcnow()
         repo_url = repo._run_in_client(["paths", "default"])
         repo_url = repo_url.strip().replace("ssh://", "https://")
         repo_url = repo_url.replace("hg://", "https://")
         cs = repo._run_in_client(["log", "-r", ".", "-T" "{node}"])
 
     url = pushlog_api_url.format(repo_url, cs)
     session = requests.Session()
     try: