We present near-infrared linear spectropolarimetry of a sample of persistent X-ray binaries: Sco X-1, Cyg X-2 and GRS 1915+105. For Sco X-1 and Cyg X-2, the polarization levels at 2.4 μm are 1.3+/-0.10 % and 5.4+/-0.7 %, respectively, which is greater than the polarization level at 1.65 μm. This cannot be explained by interstellar polarization or electron scattering in the anisotropic environment of the accretion flow. We propose that the most likely explanation is that this is the polarimetric signature of synchrotron emission arising from close to the base of the jet.