May need 'payable'?

[readytopark]

In "Keep fallback functions simple" section,

function deposit() external { balances[msg.sender] += msg.value; }

Does't this function need "payable" modifier to work properly?

[simondlr]

That is correct. Thanks @readytopark.

[ethers]

Thanks you @readytopark! Feel free to submit a pull request if you see payable missing in other areas, or if you have other improvements :)