AsyncTask.onCancelled() not being called after cancel(true)

Android SDK v15 running on a 2.3.6 device.

I'm having an issue where onPostExecute() is still being called when I am calling cancel() within a doInBackground() call.

Here is my code:

@Override
public String doInBackground(String... params) {
    try {
        return someMethod();
    } catch (Exception e) {
        cancel(true);
    }

    return null;
}

public String someMethod() throws Exception {
    ...
}

I am forcing someMethod() to throw an exception to test this out, and instead of onCancelled being called, I always return to onPostExecute(). If I check isCancelled() the returned value is true, so I know that cancel(true) is being executed.

Any ideas?