Touchpad settings are ignored (or overriden)

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On a Lenovo T550, the TapButton settings are incorrect with Fedora 22:

lesto@localhost:~$ synclient | grep TapB
    TapButton1              = 0
    TapButton2              = 0
    TapButton3              = 0

I created a 51-synaptics.conf in /etc/X11/xorg.conf.d with the right values:

Section "InputClass"
    Identifier "touchpad catchall"
    Driver "synaptics"
    MatchIsTouchpad "on"
    MatchDevicePath "/dev/input/event*"
    Option "TapButton1" "1"
    Option "TapButton2" "2"
    Option "TapButton3" "3"
EndSection

which are actually picked up by the wayland server at start up:

Aug 22 21:19:11 localhost.localdomain /usr/libexec/gdm-x-session[1805]: (**) Option "TapButton1" "1"
Aug 22 21:19:11 localhost.localdomain /usr/libexec/gdm-x-session[1805]: (**) Option "TapButton2" "2"
Aug 22 21:19:11 localhost.localdomain /usr/libexec/gdm-x-session[1805]: (**) Option "TapButton3" "3"

However, nothing actually changes in the session and synclient keeps reporting the same settings (0 for all three options). It seems there is something (maybe in gnome) that resets them at a later stage.

What can I do to make sure the touchpad settings take the intended values (apart from forcing them via synclient)?