Bukkit/Bukkit — comment on commit 4c8cd25d91cc34fbb8246efa43a7b0b2eaaa17b2
File: src/main/java/org/bukkit/plugin/RegisteredListener.java line 57
By steffengy:

Should be: if (((Cancellable) event).isCancelled() && !isIgnoringCancelled()){