diff --git a/harmony_api/scheduler.py b/harmony_api/scheduler.py
index 18726da..9a6a2a7 100644
--- a/harmony_api/scheduler.py
+++ b/harmony_api/scheduler.py
@@ -45,7 +45,7 @@
 
 
 @scheduler.scheduled_job(
-    "cron", year="*", month="*", day="*", hour="*/12", minute="0", second="0"
+    trigger="cron", max_instances=1, year="*", month="*", day="*", hour="*/12", minute="0", second="0"
 )
 def do_every_12th_hour():
     """