Unable to get property 'onMessage' of undefined or null reference in Edge extension content script

Question

I'm converting an Chrome extension which works well to Edge extension, and I need to have message listener in my content script.

Here is the code in my content script:

browser.runtime.onMessage.addListener(listener);

function listener(message) {
    console.log(message);
}

However, each time script executes, I get this error, pointing to first line of my content script code:

Unable to get property 'onMessage' of undefined or null reference

I've tried changing browser.runtime into chrome.runtime, but nothing changes.

Here I've found that Edge supports runtime.onMessage with some minor incompatibilities:

https://developer.microsoft.com/en-us/microsoft-edge/platform/documentation/extensions/api-support/supported-apis/