Vert.x 3.7.0 HttpRequest sendForm()/sendBuffer()/sendJson() methods never return if host is not available

I have a weird issue with Vert.x 3.7.0 and 3.7.1: HttpRequest send methods which transmit data in the request body (sendForm(), sendJson(), sendBuffer() etc. - all except send()) would never return, if the host is not available.

The following code never returns, if there's no server on port 4012:

        HttpClientOptions options = new HttpClientOptions()
                .setDefaultHost("localhost")
                .setDefaultPort(4012);

        Vertx vertx = Vertx.vertx();
        WebClient webClient = WebClient.create(vertx, new WebClientOptions(options));

        HttpRequest<Buffer> request = webClient.request(HttpMethod.POST, "/test");

        logger.info("Sending request as sendForm()");
        request.sendForm(MultiMap.caseInsensitiveMultiMap(), event -> {
            if (event.failed()) {
                logger.error("Failed!", event.cause());
            } else {
                logger.info("Succeeded! Code {} {}", event.result().statusCode(), event.result().statusMessage());
            }
            vertx.close();
        });

If I use request.send(event -> {...}) instead, then it prints (as expected):

27.06.19 16:47:17,352 ERROR - Failed! io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: no further information: localhost/127.0.0.1:4012
    at java.base/sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
    at java.base/sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:779)
    at io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:327)
    at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:340)
    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:632)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:579)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:496)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:458)
    at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:897)
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.net.ConnectException: Connection refused: no further information
    ... 11 more

There's no issue with Vert.x prior to 3.7.0: I tried 3.6.3, and both send() and sendForm() return with java.net.ConnectException: Connection refused: no further information. That's why I suspect it's a bug (in Vert.x, or maybe in underlying io.netty), unless I'm doing something with undefined behavior in my code.

Anybody from Vert.x community here? :)

Thanks in advance for any help.

P.S. I'm on Windows 10, Java using JVM Amazon Corretto 11.0.3.