unexpected Viper error: PredicateInstanceNoAccess

[gottschali]

Gobra reports an unexpected Viper error for the following Gobra program:

package issue

type List struct {
	next *List
	Value int
}

pred elems(l *List) {
    l != nil ==> (acc(l) && elems(l.next))
}

requires elems(l)
decreases
func foo(l *List) {
    // invariant elems(l)
    decreases elems(l)
    for l != nil {
        unfold elems(l)
        l = l.next
    }
}

Error:

13:14:39.481 [ForkJoinPool-3-worker-1] ERROR viper.gobra.reporting.FileWriterReporter - Error at: <pred_term.gobra:16:15> 
Encountered an unexpected Viper error. This is a bug. The following information is for debugging purposes:
  Accessing predicate instance might fail. There might be insufficient permission to access elems_92443cc4_F(l_V0_CN0) ([email protected])

    error is PredicateInstanceNoAccess
    error offending node = PI_elems_92443cc4_F(l_V0_CN0)
    error offending node src = Some(Info(decreases  elems(l) ,elems_92443cc4_F(l_V0_CN0),Origin([email protected],elems(l)),Vector()))
    reason is InsufficientPermission
    reason offending node = elems_92443cc4_F(l_V0_CN0)
    reason offending node src = None
        . 

    .