Conceptual modelling remains a challenging topic for educators, as it concerns ill-defined problems and requires substantial amount of practice for reaching even the initial level of proficiency. Year after year, novice modellers tend to make similar errors when learning to design models and some of those errors become persistent even at the higher level of proficiency. Are these errors the unavoidable “necessary evil” or there is a possibility to address them at the very early stage of a modeller’s education? In this work, we examine a novel approach to teaching conceptual modelling by identifying the most frequent errors in students’ models and introducing error-based step-by-step exercises in the framework of a Small Private Online Course for university students.