“Cuando llegues”: the future that is not a future tense

After cuando, en cuanto, hasta que, mientras and siempre que, Spanish uses the subjunctive when the moment has NOT arrived yet — cuando llegues, llámame — and the indicative when it is a habit or something already over: cuando llego, siempre llamo.

The usual slip. Using the present indicative for something still to come: cuando llegas, te llamo, which a Spanish speaker hears as “whenever you arrive”.

Why it catches you out. English also refuses the future here — “when you arrive, call me” — so your instinct hands you the present indicative and nothing feels wrong. The sentence that comes out is perfectly grammatical Spanish and means something else: a habit instead of a plan. Nobody corrects it, because there is nothing to correct; they just answer a question you did not ask.