NSWindowController windowDidLoad not called

I have a simple Cocoa app using a NSWindowController subclass. In the nib I have set:

• File Owner's class to my NSWindowController subclass
• The 'Window' outlet of the File's Owner to the main NSWindow in the nib.

The init method of my NSWindowController subclass is called (I call super), but not matter what I do windowDidLoad is never called.

I must be missing something obvious, but for the life of me I can't figure out what it is.