EventBus java.lang.NoClassDefFoundError

MainActivity.java

import org.greenrobot.eventbus.EventBus;
import org.greenrobot.eventbus.Subscribe;

import android.annotation.TargetApi;
import android.os.Build;
import android.support.v7.app.AppCompatActivity;
import android.webkit.PermissionRequest;

public class MainActivity extends AppCompatActivity {
    @Override
    public void onStart() {
        super.onStart();
        EventBus.getDefault().register(this);
        //Alternate, also crashes:
        //EventBus.builder().ignoreGeneratedIndex(true).build().register(this);
    }

    @Subscribe
    public void onSomeEvent(String something) {
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP) // This line makes no difference, I just added it for testing
    public void someMethod(PermissionRequest request) {
    }

    @Override
    public void onStop() {
        EventBus.getDefault().unregister(this);
        super.onStop();
    }
}