diff --git a/swh/loader/mercurial/tasks.py b/swh/loader/mercurial/tasks.py
--- a/swh/loader/mercurial/tasks.py
+++ b/swh/loader/mercurial/tasks.py
@@ -14,7 +14,7 @@
     """
     task_queue = 'swh_loader_mercurial'
 
-    def run_task(self, *, origin_url, visit_date, directory):
+    def run_task(self, *, origin_url, visit_date=None, directory=None):
         """Import a mercurial tarball into swh.
 
         Args: see :func:`DepositLoader.load`.