Unable to set the "action.threat_activity" to "1" from the advanced edit option of the saved search

Hi Splunkers, I just created a saved search and my agenda is to write the event to threat_activity index. To do this i need to enable "action.threat_activity" param to 1. But when i change the parameter to 1 and save it its not updating instead its showing as action.threat_activity=0. Is there a work around on this issue. The only thing i need is to write the saved search result to threat_activity. Kindly help ![alt text][1] [1]: /storage/temp/256609-advanced-edit.jpg