esp32: Using umqtt blocks access to webrepl

I'm using a ESP32-WROOM32 flashed with esp32-20181229-v1.9.4-762-gfa50047bb.bin.

When using umqtt in main.py with:

    c = MQTTClient('relay-board-esp32', 'example.com')
    c.set_callback(sub_cb)
    c.connect()
    c.subscribe('POWER')

    try:
        while True:
            c.wait_msg()
    finally:
        c.disconnect()

and webrepl in boot.py with:

import time
import network
import webrepl

nic = network.WLAN(network.STA_IF)
nic.active(True)
nic.connect('wifi', 'password')

while not nic.isconnected():
    time.sleep(1)

print('Connected to WiFi!')
print(nic.ifconfig())

webrepl.start()

no further connections via webrepl are possible.

Is this intended? Is there a solution or work around?
I thought the webrepl is listening in the background for new connections, but as soon as I run umqtt, webrepl does not accept new connections any more.

Does this mean no simultaneous access to webrepl and mqtt subscriptions is possible?

Reproduce the setup using main.py with umqtt and boot.py with webrepl on an ESP32, starting with the shown c.wait_msg() loop and webrepl.start() entry points. Check whether simultaneous MQTT subscriptions and webrepl connections are supported; done means either both connections work or the limitation and workaround are documented.