Formally <cite>HyTER</cite> is defined as: where Y is a set of references that can be encoded as a finite state automaton such as the one represented in Figure 1 , x is a translation hypothesis and LS is the standard Levenshtein distance, defined as the minimum number of substitutions, deletions and insertions required to transform x into y. We use, in all our experiments, our own im-plementation of <cite>HyTER</cite> 1 that relies on the Open-FST framework (Allauzen et al., 2007) .