Accurate spelling matters for L2 learners: It facilitates communication, affects other aspects of the writing process, and is an important assessment criterion. However, even in phonologically transparent writing systems like Spanish, L2 learners experience spelling difficulties. Nonetheless, explicit spelling instruction appears to be neglected by L2 teachers. Synchronous written corrective feedback, provided automatically by computerised spellcheckers, is one way of providing such instruction without cost to teaching time. However, evidence concerning the effectiveness of such feedback is mixed. Further, existing spellcheckers, designed for L1 speakers, present various problems for L2 learners. The current study reports on an experimental trial of a Pedagogic Spellchecker (PSC), developed specifically for L2 learners. In all, 107 adult learners of Spanish as a Foreign Language were block randomised into three treatment groups. All groups completed a short transcription task on five consecutive days. One group received feedback from the PSC; another received feedback from Microsoft Word spellchecker; the third received no feedback. Pre- and post-test data showed that the PSC group progressed significantly more in spelling accuracy than the other groups, with a large effect size. Nonetheless, Microsoft Word spellchecker reduced errors on spelling forms that it did not autocorrect. Pedagogical and theoretical implications are discussed.