Add 2 lengths of shrink-tube on the 2 wires.

Now, solder the 4 wires together.

Alternatively, you could just use duct tape—just be careful so it doesn't slide off when you're bending the wires.

Move the shirk-tube over the soldering spots, and heat it up. (Mine fell a bit short, so I did end up using a bit of duct tape.)