Error While Configuring MQTT event bus

Hi I Have follwed insturction for configuring mqtt event bus in my openhab

my mqtt-eventbus.cfg looks like this;-

mqtt-eventbus:broker=
mqtt-eventbus:commandPublishTopic=/openHAB/out/${item}/command
mqtt-eventbus:stateSubscribeTopic=/openHAB/in/${item}/state

But I am getting this following error :-

Could not create event bus state subscriber: Configuration ‘:/openHAB/in/+/state:state:default’ is not a valid inbound configuration: Configuration requires 4 or 5 parameters separated by ‘:’