  CoKu Tau/4 has been labeled as one of the very few known transition disk
objects: disks around young stars that have their inner disks cleared of dust,
arguably due to planetary formation. We report aperture-masking interferometry
and adaptive optics imaging observations showing that CoKu Tau/4 is in fact a
near-equal binary star of projected separation $\sim$53 mas ($\sim$8 AU). The
spectral energy distribution of the disk is then naturally explained by inner
truncation of the disk through gravitational interactions with the binary star
system. We discuss the possibility that such ``unseen'' binary companions could
cause other circumbinary disks to be labeled as transitional.
