Rule: Add action "Add a comment to the order" undefined uc_order_action_comment_types

To see, when which rules fires, I just wanted to add comments to the order (so that I can see which of the rules are executed).
Picking a random rule "E-mail admin checkout notification".
"Add action" and choose "Add a comment to the order"

Then an AJAX-Error-Popup occurs with:
Fatal error: Call to undefined function uc_order_action_comment_types() in .../modules/rules/ui/ui.data.inc line 134

I'm using Rules 7.x-2.0-alpha5