diff --git a/icinga2api/actions.py b/icinga2api/actions.py
index e6dfae8..079a4e9 100644
--- a/icinga2api/actions.py
+++ b/icinga2api/actions.py
@@ -480,7 +480,7 @@ def schedule_downtime(self,
         }
         if filter_vars:
             payload['filter_vars'] = filter_vars
-        if fixed:
+        if not fixed:
             payload['fixed'] = fixed
         if trigger_name:
             payload['trigger_name'] = trigger_name