In simultaneous interpreting studies, the concept of interference -- namely, the marks of the source language in the target language -- is perceived as a negative phenomenon. However, interference is likely to happen at a lexical level when the target language does not have its own lexicon. This is the case in international sign (IS), which can be defined as a mix of different sign languages, in which the lexical items are not fixed. This qualitative study analyses a dataset of interpretation from Sign Language of the Netherlands (NGT) to IS by a team of two Dutch, deaf interpreters at an international conference in Nijmegen, the Netherlands. We observed the occurrence of source NGT lexical items borrowed into the IS target output and considered the strategies used in this. The phenomenon was found to be recurrent. In addition, depending upon the type of lexical items, the strategies used to borrow NGT lexicon were found to differ. Thus, we have described the set of strategies and examined the results in comparison with previous findings. As a practical output, this study could inspire current and future IS interpreters to expand their set of interpreting strategies.