[O] cannot export to beamer.

[Uwe Brauer]

Hi

I am very used to the beamer style and it works on my machine quite
well. 

Now I took the example
https://orgmode.org/manual/A-Beamer-example.html#A-Beamer-example

And wanted to export it to beamer but obtained the message 
user-error: Unknown LaTeX class ‘beamer’

Which leaves me puzzled. 

I am running Ubuntu 16.04 and have installed the latest org form master.
GNU Emacs master as well.

Any ideas?

Uwe Brauer