sudo update-alternatives --set glx /usr/lib/nvidia
# Use special xorg.conf and pass NVIDIA_DIRECT directive to .xinitrc.
-NVIDIA_DIRECT=1 startx -- -config xorg.conf.alt
+NVIDIA_DIRECT=1 startx -- -config xorg.conf.forced_nvidia
# Recreate bumblebee setup.
sudo service bumblebeed start