The defender netted in the 86th minute against Celta Vigo at Campo de Fútbol de Mendizorrotza, following in to force home from close range after his initial header had hit the bar.
But the struggling Babazorros were already 3-0 down and Lejeune's goal was a mere consolation. Alavés are currently bottom in Spain's top flight.
On Easter Monday, Freddie Woodman played the whole game in goal as Swansea were beaten 1-0 at home by Preston North End in the Sky Bet Championship, while Kell Watts completed another 90 minutes for Plymouth Argyle in their 3-0 defeat to Shrewsbury Town in League One.
And in the National League, Hartlepool drew 2-2 at Boreham Wood - a 13th game unbeaten - with Lewis Cass making his 28th appearance of the campaign.