(Set ℓ) != Set in closures.agda when trying to compile IAL

[shingarov]

(I am an absolute newcomer here who doesn't know what he is doing.) I am trying to read @astump 's book, and as the first step I am trying to make IAL:

$ agda --version
Agda version 2.6.3
$ git clone https://github.com/cedille/ial.git
$ cd ial
$ make
…
/home/boris/work/ial/closures.agda:20,21-31
(Set ℓ) != Set
when checking that the solution A of metavariable _A_22 has the
expected type Set
make: *** [Makefile:36: combinators.agdai] Error 42
$

Help?