MQTT Binary Sensor for LCD display backlight never shows "ON"

Hi there,
I am running out of ideas to get the MQTT Binary Sensor for the Tinkerforge LCD display backlight to work. It just stays all the time off although the LCD backlight is on.

However, here is my configuration and the results of my testing:
Excerpt of my configuration.yaml:

 binary_sensor:
  - platform: mqtt
    state_topic: "tinkerforge/bricklet/lcd_20x4/ofH/backlight_on"
    name: "LCD Status"
    payload_on: "true"
    payload_off: "false"
    value_template: '{{ value_json.backlight }}'

Testing the state topic via Mosquitto:
mosquitto_sub -t tinkerforge/bricklet/lcd_20x4/ofH/backlight_on
yields results in JSON format reflecting the true state of the LCD display backlight:

{“backlight”:true,"_timestamp":1503218724.4418452}
{“backlight”:false,"_timestamp":1503218771.6261723}
{“backlight”:true,"_timestamp":1503218778.034893}

Perhaps I missed something in the configuration or the MQTT-stuff, so any hint is very welcome.
Thanks in advance,
topi

Finally, I found the solution here in the Home-Assistant Forum. I had to remove the quotes around true and false, so that the working configuration looks now this way:

binary_sensor:
   - platform: mqtt
     state_topic: "tinkerforge/bricklet/lcd_20x4/ofH/backlight_on"
     name: "LCD Status"
     payload_on: true
     payload_off: false
     value_template: '{{ value_json.backlight }}'