Error: An error occurred while retrieving a new session: "invalid argument: 'capabilities' must be a JSON object"

[jmervis99]

Hi,
I am getting the following error when I set w3c to true. I am using nightwatch 2.1.5

Error: An error occurred while retrieving a new session: "invalid argument: 'capabilities' must be a JSON object"

My desiredCapilities look like

    "desiredCapabilities": {

      "browserName": "chrome",
      "javascriptEnabled": true,
      "acceptSslCerts": true,
        "goog:chromeOptions": {
          "args": ["--no-sandbox", "--disable-features=VizDisplayCompositor","--user-agent=test","--headless"
          
        
          
       ],
          "w3c": true,
         
 
          "prefs": {
            "addCustomRequestHeader":"true",
          "protocol_handler": {
              "excluded_schemes": {
              "fasp": false}
              }
            } 

        
        }
     
    },

Any advice is appreicated.