Error while proxying to blog subdomain from node.js app

I have a nodejs app hosted on heroku at www.example.com Then I have a wordpress blog, currently on a subdomain - blog.example.com

I have a route setup in express:

(using express-http-proxy )

var proxy = require('express-http-proxy');

app.use('/blog', proxy('blog.example.com', {
    forwardPath: function(req, res) {
        return require('url').parse(req.url).path;
    }
}));

      

        
        
        
      

    

This works in the sense that I can see the blog homepage at www.example.com/blog - it proxies correctly and transparently to blog.example.com

However, if I go to any of the blog posts it crashes with a 500 error

[error] [client (ipAddressHere)] The request exceeded the 10 internal redirects limit due to a possible configuration error. Use "LimitInternalRecursion" to increase the limit if needed. Use "LogLevel debug" to get backtrace., Referer: http://www.example.com/blog/

I suspect it has something to do with my htaccess - but can't figure out what?

My htaccess:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /blog/
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /blog/index.php [L]
</IfModule>

# END WordPress