Create a trigger based on icmp template for instance (set the 'allow manual close' checkbox in trigger template definition first)

configure a host with this template to generate an event (wrong ip for instance)
Using API event.get , get the event id related to this problem
Using API event.acknowledge, provide eventids, message and action set to 1.
Zabbix returns following message:
Only trigger events can be acknowledged

This event is coming from trigger, so I don't understand why using this API it's not possibel to close events.
Regards,
Marc

Result:
See screenshot...
See log file...
See memory dump...
Expected:
See screenshot...
See attached patch file...