Disaster Effect don't vanish when the disaster ends?

[neondt]

    add_disaster_modifier = {
       name = "domestic_improvements"
       duration = -1
       disaster = internal_conflicts
     }

Looks like it's supposed to disappear when the disaster ends. If it were when your ruler dies, it'd be a ruler modifier. How long has it been since the disaster ended?

 

[neondt]

Abt 10 Years?

Could be a bug then.