Setting up multisite on OS X / El Capitan / MAMP Pro

I've recently swapped from AMPPS to MAMP Pro. Most things are working fine. But when I set up a new multisite, at the point where I edit my htaccess and wp-config files, and save the settings, WordPress starts showing the "Error establishing a database connection" message.

Any ideas what steps I might be missing out?

[edit] Problem was me all along - I was missing out the line: "define('MULTISITE', true);" Sorry for this, but I'll leave my silliness here in case it helps anyone else!