GeoDjango - syncdb或南迁移错误

Question

有人见过这个错误吗？我的迁移失败了：（

django.db.utils.DatabaseError: function addgeometrycolumn(unknown, unknown, integer, unknown, integer) is not unique
LINE 1: SELECT AddGeometryColumn('maps_mapfeature', 'geom', 4326, 'M...
               ^
HINT:  Could not choose a best candidate function. You might need to add explicit type casts.

这是模型

class MapFeature(models.Model):
    source = models.ForeignKey('MapLayer')
    label = models.CharField(max_length=255, blank=True)
    muni = models.CharField(max_length=255, blank=True)
    description = models.TextField(blank=True)
    geom = models.MultiPolygonField(srid=4326)
    objects = models.GeoManager()

    def __unicode__(self):
        return self.label