AttributeError using inheritance with 2 ImageSpec

imagekit-inheritance-attribute-error.py

class BaseImage(models.Model):
    original_image = ProcessedImageField(null = True, blank = True, upload_to='static/original',)
    admin_thumbnail = ImageSpec([Adjust(contrast=1.2, sharpness=1.1),
            resize.Crop(50, 50)], image_field='original_image', options={'quality': 90})
    def __unicode__(self):
        return u"%s" % (self.original_image)
    class Meta:
        abstract = True
        
class FirstTest(BaseImage):
    image_first = ImageSpec([Adjust(contrast=1.2, sharpness=1.1), resize.Crop(200, 200)], image_field='original_image', options={'quality': 90})

class SecondTest(BaseImage):
    image_second = ImageSpec([Adjust(contrast=1.2, sharpness=1.1), resize.Crop(400, 400)], image_field='original_image', options={'quality': 90})



The error tryng to add a 'Second Test':

Django Version:	1.3.1
Exception Type:	AttributeError
Exception Value:	'SecondTest' object has no attribute 'image_first'
Exception Location:	...../testimagekit/imagekit/utils.py in get_spec_files, line 33