Converting MQTT data from C to F

After a few days work I now can access my Flair vent data in HA using an MQTT broker.

Flair transmits all temperature as C and I want to present it as F. I thought I could use a template but am doing something wrong.

# HVAC Flair vents and pucks
  - platform: mqtt
    name: "Master Bedroom"
    current_temperature_topic: "homeassistant/sensors/flair/puck/Master Bedroom-a30f/Temperature"
    current_temperature_template: "{{(value * 9/5)+32}}"
    precision: 0.1

Without the template line the correct C value shows up. But with the template line, I get nothing.

Help this noob please!

Got it working with a slight modification to the template.

    current_temperature_template: "{{(float(value_json) * 9/5)+32}}"