isSynthetic() returns false for lambda instances

The JCK8 compiler tests lmbd063* check the following assertion of JSR335 v0.6.1:

15.27.4 Run-time Evaluation of Lambda Expressions [New]
...
"The value of a lambda expression is a reference to an instance of a synthetic class with the following properties:"

The tests failing are (jck8b18, jdk8b78):

lang/LMBD/lmbd063/lmbd06301m0/lmbd06301m0.html
lang/LMBD/lmbd063/lmbd06301m1/lmbd06301m1.html
lang/LMBD/lmbd063/lmbd06301m2/lmbd06301m2.html
lang/LMBD/lmbd063/lmbd06301m3/lmbd06301m3.html
lang/LMBD/lmbd063/lmbd06301m4/lmbd06301m4.html
lang/LMBD/lmbd063/lmbd06301m5/lmbd06301m5.html

The tests report error message at run-time:

Not synthetic lambda class