MethodHandles.Lookup.findVirtual() throws IllegalAccessException if the method MH is being created for is private and declared in an interface.

Example:
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;

public interface PrivateInterfaceMethodLookupTest {
    public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException {
        MethodHandles.lookup()
                .findVirtual(PrivateInterfaceMethodLookupTest.class, "m", MethodType.methodType(void.class));
    }

    private void m() {}
}

Output:
Exception in thread "main" java.lang.IllegalAccessException: no such method: PrivateInterfaceMethodLookupTest.m()void/invokeInterface
        at java.lang.invoke.MemberName.makeAccessException(MemberName.java:869)
        at java.lang.invoke.MemberName$Factory.resolveOrFail(MemberName.java:990)
        at java.lang.invoke.MethodHandles$Lookup.resolveOrFail(MethodHandles.java:1382)
        at java.lang.invoke.MethodHandles$Lookup.findVirtual(MethodHandles.java:858)
        at PrivateInterfaceMethodLookupTest.main(PrivateInterfaceMethodLookupTest.java:7)
Caused by: java.lang.IncompatibleClassChangeError: private interface method requires invokespecial, not invokeinterface: method PrivateInterfaceMethodLookupTest.m()V
        at java.lang.invoke.MethodHandleNatives.resolve(Native Method)
        at java.lang.invoke.MemberName$Factory.resolve(MemberName.java:962)
        at java.lang.invoke.MemberName$Factory.resolveOrFail(MemberName.java:987)
        ... 3 more