world.getChunkAt().isLoaded() is unknown

Hey guys,
I tried doing some stuff with blocks but sometimes it comes to unloaded/uncreated chunks
the problem is Chunk.Load and Chunk.isLoaded both return this error:

Code:

17:37:26 [SCHWERWIEGEND] Exception in thread "Thread-7"
17:37:26 [SCHWERWIEGEND] java.lang.NoSuchMethodError: org.bukkit.Chunk.load(Z)Z
17:37:26 [SCHWERWIEGEND]        at me.kostronor.bukkitbenchmark.tasks.Task_World.run(Task_World.java:42)
17:37:26 [SCHWERWIEGEND]        at org.bukkit.craftbukkit.scheduler.CraftWorker.run(CraftWorker.java:34)
17:37:26 [SCHWERWIEGEND]        at java.lang.Thread.run(Unknown Source)

well, thats where i got lost