hook_userpoints does not fire after userpoints_rules actions

I am currently experiencing an issue with the userpoints_rules action "Grant points to user". While this functionality works, it does not seem to invoke hook_userpoints() so that my module can act on the points transaction. If this is expected behavior, is there any way to work around it? If this is a bug in userpoints_rules, I will submit a patch that will fix the problem. Thanks in advance!