Pi Gnome on screen keyboard special characters

This might be a bit of specific issue I’m having, but on a Pi I have Gnome running, with the On Screen Keyboard. It looks great, and works well, except for special characters like é or ü and such.
When I press and hold for instance u, the ü does show, but when I click it (on the touchscreen or when using the mouse) no character is added. Does anyone know how to get these special characters to work?