How to modify the dictionary

[c856450]

echo 艷 | opencc -c t2s.json
outputs the correct character 艳.

However when doing the reverse action with
echo 艳 | opencc -j s2t.json
the output is 豔.

Apparently 艷 and 豔 are both correct.

This leads to the question: how do I modify my local dictionary customizing the output of particular character. In this case, I wish to have the output 艷 instead of 豔, even the latter appears to be more appropriate.

Can someone help me here?