case-insensitive regexp in derived-mode

[jfjfcli]

Following this tutorial
http://ergoemacs.org/emacs/elisp_syntax_coloring.html

Now my keywords are working, but the regexp to colour keyword is case 
insensitive.

I was able to get it to work by evaluating
(setq font-lock-keywords-case-fold-search t) 
after loading the custom mode into that buffer.

However no matter where I put it in the .el file of the custom mode, I cannot 
to work automatically.

The documentation also says "You can use case-fold in font-lock-defaults to 
specify the value of font-lock-keywords-case-fold-search which says whether 
search-based fontification should be case-insensitive."

any help would be great, thanks.