Hi, I am working for a company that uses a proprietary Scheme based language The language has a rich API and its own conventions, so I created a new major mode but I am struggling with fontification: I have elisp functions to fetch all documented functions and user-defined functions from my code and add them properly to font-lock-defaults (using regexp-opt) Everything was working fine while I was fetching keywords from a very limited number of modules. But now I am using more of them and I have hundreds (maybe thousands) of keywords to highlights. Now that I added more functions to font-lock-defaults nothing is highlighted anymore. I really need to add those modules and I definitely require fontification as I am too used to it. I don't want to replace keywords with more global regular expressions as it is really helpful to have keywords highlighted only when they are written properly I took a quick glimpse at font-core.el and font-lock.el but I could not find where the regexp match limitations are set Do you have a solution or an idea to increase the limits of keywords that can be matched by font-lock-mode ? I would be extremely grateful if you can help me Regards, Aurélien Buchet