Can't get 'max-load-*' feature to work with `watchdog`

I can't seem to get watchdog's 'max-load-*' features working on Ubuntu 14.04 (in a Vagrant VM w/ Virtualbox).

From my understanding, it should be fairly straight forward. Here's how I'm testing it.

• I've set 'max-load-1' to 0.5 for testing purposes (and added -v -f to the start params) [1]
• Restart the watchdog service (service watchdog restart)
• Triggered burnP6 to simulate a heavily loaded server (the test VM only has one core, so it spikes pretty fast)

The expected result (to me) would be that the box would reboot after load average reaches 0.5, but it just goes on plateaus at around 1.

I've also experimented with the 'ping' feature, and that one works just like a charm. If I set it, and then removes the default gateway, the VM reboots as expected.

I've also tried adding the 'softdog' module and explicitly set 'watchdog-device = /dev/watchdog', but it doesn't seem to make any difference.

Am I missing something?

[1] watchdog.conf: https://gist.github.com/vpetersson/8487f45826216f556e89