Top: SED of a new BL Lac candidate, ID = 2440. Red circles display WISE and dereddened 2MASS flux densities. The SDSS dereddened spectrum is shown in blue. Gray lines represent two SWIRE templates of a 13 Gyr old elliptical galaxy normalized to the W2 band (solid) or to the SDSS spectrum (dotted). The departure of the SDSS spectrum from the latter template highlights the reduced Dn(4000) value of the source, while the W3 (and W4) excess appears from the comparison of the WISE data with the first template. Bottom: rest-frame SDSS spectrum with indication of the main AGN emission lines (upper labels) and galactic absorption lines (lower labels).