[1.8] instrumentation fails

The following piece of code fails to be instrumented

List<String> s = new ArrayList<>();
String.join(", ", s.stream().map(e -> "'" + e + "'").collect(Collectors.toSet()));

With this error
[ERROR] /Users/kasperni/workspace/cake-container/cake-util/cake-util/target/clover/src-instrumented/org/cakeframework/internal/util/ValidOptions.java:[40,52] no suitable method found for join(java.lang.String,java.util.Set<java.lang.Object>)
[ERROR] method java.lang.String.join(java.lang.CharSequence,java.lang.CharSequence...) is not applicable
[ERROR] (varargs mismatch; inference variable R has incompatible bounds
[ERROR] equality constraints: java.util.Set<java.lang.Object>
[ERROR] upper bounds: java.lang.CharSequence,java.lang.Object)
[ERROR] method java.lang.String.join(java.lang.CharSequence,java.lang.Iterable<? extends java.lang.CharSequence>) is not applicable
[ERROR] (argument mismatch; inference variable R has incompatible bounds
[ERROR] equality constraints: java.util.Set<java.lang.Object>
[ERROR] upper bounds: java.lang.Iterable<? extends java.lang.CharSequence>,java.lang.Object)