GST_VAAPI_DRM_DEVICE don't work

I try to restrict the gst-vaapi run on special device with GST_VAAPI_DRM_DEVICE
But in test, if I setup GST_VAAPI_DRM_DEVICE with the error value like GST_VAAPI_DRM_DEVICE=/dev/dri/renderD64
the command line can still worked, so it look GST_VAAPI_DRM_DEVICE is not worked
Already try with gst-vaapi sample command line

So I need someone to help me to point how to restrict the test device