Confusion regarding direction of kinetic friction on inclined plane.

please help!

The formula for kinetic friction acting on a sliding body is

μ_kN

When the body is sliding with constant velocity down an inclined plane

f_k=μ_kN

When the body is sliding up the inclined plane(say due to a force acting parallel to the inclined plane) with constant velocity

even then

f_k=μ_kN

The direction of kinetic friction is opposite in the 2 cases

while the formula for f_k is exactly the same.

If friction is a vector shouldn't the formula for kinetic friction account for its direction too?