how to reference environment variable from devcontainer when vscode connected to remote machine via ssh

When I'm running a devcontainer in vscode on my local machine, propagation of environment variables from host works as described in docs using localEnv syntax in devcontainer.json:

{ 
...
 "remoteEnv": {
   "MY_VAR": "${localEnv:MY_VAR}"
 }
}

However, when I'm connecting from vscode to remote machine via ssh and open devcontainer there, localEnv uses value from my client machine, where vscode UI is running, and not from remote machine to which I'm connected via ssh.

Is it possible to somehow access/propagate remote machine's environment variables from devcontainer?