Nightwatch.JS unknown command: Cannot call non W3C standard command while in W3C mode

Hey I'm new to nightwatch.js, i've been trying to get browser.getElementSize to work with my nightwatch.js setup. Every time i try run the test i get errors saying W3c doesn't like it.

I've tried to add w3c equals false to my config file, but no matter where i put it, it still doesn't work.

desiredCapabilities: { browser: "chrome", "javascriptEnabled" : true, "acceptSslCerts" : true, name: "Chrome-[Nightwatch] Sample Test", chromeOptions: { w3c: false } }

i get two error messages

Error while running .getElementSize() protocol action: unknown command: Cannot call non W3C standard command while in W3C mode

and

TimeoutError: An error occurred while running .getElementSize() command on <#bedrooms>: