How time constant is equal to (L/R)?

We know that the series RLC circuit has time constant T=L/R The units on LHS is sec.But the unit on RHS is henry/ohm.so how these two are equal?

we know that  L= V/(di/dt)

and R= V/I

L/R={V/(di/dt)}/(V/i)

so th units of L/R is seconds.