Server_timer doesn't work

[avertusss 9]

Hi. I want to make mobs waves in dungeon but i have problem with server_timer.

		when login with is_in_dungeon(130) begin
			if not d.is_joinable() then
				d.notice("Bye bye")
				pc.warp_exit()
				return
			end
			
			if d.getf("stage") == 0 then
				d.setf("stage", 1)
				notice_mission("Kills mobs")
				d.regen_file("data/dungeon/dungeon_75.txt")
				d.setf("mobs", 100)
				server_timer("dungeon_wave_2", 5)
			end
		end
		
		when dungeon_wave_2.server_timer begin
			d.notice("Kill mobs from second wave")
			d.regen_file("data/dungeon/dungeon_75.txt")
		end

Server_timer doesn't work. How should i make that? Normal timer works properly.