How can I make CTRL+N select the next match in a GTK+ GtkComboBox

I have a GtkComboBox with a GtkEntryCompletion setup the GtkEntry object. When I start typing in the GtkEntry, it shows a pop-up of the items that match what's been typed so far. I can then press the down arrow to select the first match.

My question is can I setup the GtkEntry/GtkCompletion somehow to enable Ctrl+n in addition of the down arrow and Ctrl+p in addition to the up arrow.

Chrome's address bar (at least on MacOS) works like this. You can type something and press Ctrl+N to get to the next match. I'd like to implement the same UI design in my GTK+-2 app.