Unwanted increments of the Issue ID

I would like to check required custom fields. However each time the reporter attempts to create an issue without filling in the required fields the issue ID increments.

Steps to reproduce:

step 1: apply the following rule:
when becomesreported() {
;
}

step 2: fill in summary
step 3: press Create issue
step 4: repeat step 3 several times
step 5: fill in 'Fix versions'
step 6: create issue
step 7: observe the ID of the created issue

expected: ID is last created ID + 1
actual  : ID is last created ID + # of attempts to create