react solidity event memory leak

I am getting solidity events from componentdidmount with the following code:

myDataSocks.events.ReceivedPayment({}, async (error, event) => {
if (!error) {
const account = event.returnValues.fromAcct;
const payment = web3.utils.fromWei(event.returnValues.payment);

console.log('ReceivedPayment: ', account, payment);
this.notify(`You received ${payment} ether from ${account}`);

let contractBalance;
await web3.eth.getBalance(address).then(function(result) {
contractBalance = web3.utils.fromWei(result);
});

this.setState({ contractBalance });

} else {
console.log('ReceivedPayment error:', error);
}
});


However, sometimes I am getting this error:

warning.js:33 Warning: Can't call setState (or forceUpdate) on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in the componentWillUnmount method.
in privateData (created by App)

Looks like I need to stop listening for solidity events in componentwillunmount. Does anyone know how to do that?

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