Cfengine 3 error: Redefinition of body \"control\" for \"common\" is a broken promise, near token '{'

I tripped across this error today with Cfengine 3:

cf3:./inputs/promises.cf:1,22: Redefinition of body "control" for "common" is a broken promise, near token '{'

The weird thing was this was a stripped down promises.cf, and I could not figure out why it was complaining about redefinitions. I finally found the error:

body common control {

bundlesequence => { "test" };
inputs => { "promises.cf", "cfengine_stdlib.cf" };

}

Yep, including the promises.cf file itself in the inputs section borked everything; removing it fixed things right away.