Spot the deliberate mistake

Got caught out today doing some Jave code at work.

I thought I'd be a good boy and use Commons Lang utilities to implement toString(), hashCode() and equals(). Spot the mistake here:

@Override
public int hashCode() {
    return new HashCodeBuilder(13, 73).append(field1).append(field2).hashCode();
}

Any ideas? Here's the corrected version:

@Override
public int hashCode() {
    return new HashCodeBuilder(13, 73).append(field1).append(field2).toHashCode();
}

An easy mistake to make when using an IDE with auto-complete.

Luckily I was saved by my unit tests!