Json Template - Parsing Error

I have a window sensor with the following mqtt message:
{“node_data”: {“hostname”: “ESP826612E-2-Dario-Bedroom”, “mac-address”: “60019438A8C6”}, “windowstate”: Open}

But somehow home assistant is not able to parse it and I get the following error:
Error parsing value: ‘value_json’ is undefined (value: {“node_data”: {“hostname”: “ESP826612E-2-Dario-Bedroom”, “mac-address”: “60019438A8C6”}, “windowstate”: Open}, template: {{ value_json.windowstate }})

The code in the configuration file looks like this:
- platform: mqtt
state_topic: “myhome/dariobedroom/windowstate”
name: ‘Window State Dariobedroom’
value_template: ‘{{ value_json.windowstate }}’

What could cause this issue?

I’d imagine that Open should be quoted to be valid Json?

It worked! Thanks .
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