NPE generating serializedLambdaName for nested lambda

The following test generates an NPE:

import java.io.*;
import java.util.Map;
import java.util.HashMap;

public class LambdaLambdaSerialized {

    static int assertionCount = 0;

    static void assertTrue(boolean cond) {
        assertionCount++;
        if (!cond)
            throw new AssertionError();
    }
    
    public static void main(String[] args) throws Exception {
        try {
            // Write lambdas out
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutput out = new ObjectOutputStream(baos);
            LSI<LSI<Map>> ssi = () -> (() -> new HashMap());
            write(out, ssi );
            out.flush();
            out.close();

            // Read them back
            ByteArrayInputStream bais =
                new ByteArrayInputStream(baos.toByteArray());
            ObjectInputStream in = new ObjectInputStream(bais);
            readAssert(in, "[X]");
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
            throw e;
        }
    }

    static void write(ObjectOutput out, LSI<LSI<Map>> lamb) throws IOException {
        out.writeObject(lamb);
    }

    static void readAssert(ObjectInputStream in, String expected) throws IOException, ClassNotFoundException {
        LSI<LSI<Map>> ls = (LSI<LSI<Map>>) in.readObject();
        Map result = ls.get().get();
        System.out.printf("Result: %s\n", result);
    }
}

interface LSI<T> extends Serializable {
    T get();
}