We measured the angular dependence of the irreversible magnetization of a YBa2Cu3O7 single crystal with columnar defects (CD) inclined with respect to the c-axis. At temperatures T greater than or equal to 40K and high fields we observe a sharp maximum centered at the tracks' direction. At T less than or equal to 20K the behavior is quite different. At high fields a broad bump at the tracks' direction is still visible, but its height is small and it appears only as a perturbation to the angular dependence due to material anisotropy. However, by performing the usual anisotropic rescaling (Blatter et al., Phys. Rev. Lett. 68, 875, 1992) we recover the strong unidirectional effects due to CD's.