socket.io: Node.js app error when loading Socket.Io

I am running Node.js (Centos 7) and I just started to implement Socket.io.

The only line of code I have regarding Socket.io is in my /bin/www file

var io = require('socket.io')(server);

The app blows up with an error:

error Cannot find module ‘bufferutil’

I have done

npm install bufferutil --save

but does not fix the issue.