declarativeNetRequest rule ignored for mixed-content requests

Question

I'm trying to avoid blocking mixed-content by upgrading requests scheme to https using the declarativeNetRequest API.

With the following basic rule:

{
    condition: {
        excludedResourceTypes:['ping']
    },
    action: {
        type:'upgradeScheme'
    }
}

It seems to work only for main_frame requests while insecure sub_frame requests are being blocked immediately without attempt to upgrade.

Mixed Content: The page at https://localhost.com was loaded over HTTPS, but requested an insecure script http://localhost.com/script.js - This request has been blocked; the content must be served over HTTPS.

Is there a way around this?