How can I have access to the Authorization header inside a request interceptor in Axios?

I have this code

axiosInstance.interceptors.request.use(
    async config => {
        const headers = config.headers;
        console.log('headers' , headers);
        console.log('headers', headers.Authorization);

return config ;
});

the first log I can see the Authorization header in the object :

headers {
“Accept”: “application/json, text/plain, /“,
“Authorization”: “Bearer abc123”
}

but the second log, Authorization is undefined :

headers undefined

How can I have access to the Authorization header inside a request interceptors in Axios?