Crash with "get-value": "Can't compute ground term ..."

Running Colibri2 on the following example:

(set-logic ALL)

(declare-const x Int)
(declare-const y Bool)

(assert y)
(check-sat)
(assert (> x 0))
(check-sat)
(get-model)
(get-value (x))

Results in a crash due to an uncaught exception:

sat                                     
sat
(error "Error Uncaught exception:
              Can't compute ground term x of type int.
...

Removing the first (check-sat) results in the right output.