The field of a test charge at rest in a plasma is known to be shielded via the collective interaction between the test charge and the particles of the plasma. In a thermal equilibrium plasma, the shielded potential has a spatial variation of the Debye form exp (— r)/r. In this note we will show that, in a collisionless current-carrying plasma, the potential profile along the radial direction parallel to the current changes from the Debye form to a potential well form, and causes a reversal of the ele ctric field of the test charge. The formation of the Debye potential well is attributed to the resonant interaction between the particles and the waves stationary in the test charge frame when the net flux of charged particles is different from zero. This is the same type of resonant interaction which leads to the well-known Landau damping (Landau 1946).