Comment # 12 on bug 98146 from Michel Dänzer

I suspect the intel driver only supports the

 Option "DRI" "3"

notation to enable DRI3 at runtime. If that doesn't work:

* Make sure the Section "Device" with that option is actually being used
* Make sure that DRI3 is enabled in the xf86-video-intel build; if in doubt,
try
  passing --enable-dri3 to its configure script