[Agda] font issue in emacs mode

[Martin Escardo]

I am using ubuntu 14.04.1 with Agda 2.4.2 via cabal. Works fine.

However, some fonts don't display correctly. For example, \b1 
(blackboard one) displays as some hexadecimal numbers in a box.

Such symbols display ok with the same version of Agda but in ubuntu 12.04.

Does anybody know how to solve this for ubuntu 14.04? I suspect there is 
a missing ubuntu package that I should install.

Thanks,
Martin