The central region of M87 in the K′ (2.1 μm) - band was imaged using the 2.2m telescope on Calar Alto, Spain. In addition to the jet our K′ exposure (Fig. 1) shows an arclike structure ∼ 24 arcsec southeast of the nucleus. This is the IR counterpart to the feature detected by Stiavelli et al. (1992) in the optical and to the brightness maximum of the southeastern radiolobe designated as “theta” (Hines et al. 1989). Its radio to IR spectral index is α = −0.88 ±0.01 (Sv ∞ v α), consistent with the radio spectral index of α = −0.84 ± 0.07 (Salter et al. 1989) of the whole radio lobe measured between 5 GHz and 230 GHz.