dzn 2.12: internal-error when trying to access a field on a boolean

In the following model: bug1.dzn on a boolean variable, a field is selected which gives an internal error: internal error: /home/paul/bug1.dzn: goops-error: (#f "No applicable method for ~S in call ~S" (#< ast:field* (2)> (ast:field* (bool** (scope.name-node* ("bool"))))) ())