In this thread, it is accepted that answers that use a new version of a language created after the challenge was posted are non-competing, because otherwise people would implement new built-ins that fit the challenge.
However, it is not clear in this answer (and @lirtosiast comment is not answered) whether or not a bug fix of the implementation of a language is considered a "new version" or not.
It is pretty common for me to find bugs in my own language while trying to answer a challenge.
Assuming good faith of the user (i.e. that he really intented his language to work that way in the first place), is it acceptable to fix bugs in a language's implementation after the challenge was posted, while keeping the "competing" status of the answer?