How to send postMessage to iframe from parent page

Question

I'm trying to send a message to iframe from the page, but it seems like this message does not received. Code from the page:

let iframe = document.getElementById('myiframe')
iframe.contentWindow.postMessage('message body', window.location.origin)
console.log('message sent')

Code from the iframe:

window.addEventListener('message', function(m){
  console.log(m)
}, false)

So, in the console I see only the first part - 'message sent', what can be the reason of this issue? Site and iframe have different domains