Jenkins multibranch pipeline job CHANGE_ID not set - github

Question

I have setup a job with Jenkins with MultiBranch pipeline.
Github is the SCM and is configured, with a webhook to fire a build on a PR commit. (Existing or new PR).
The build is triggered, all goes fine 1, however the CHANGE_ID is not set (null). We need the CHANGE_ID to pass on to Sonar.
I am struggling to understand, in which cases this parameter is set, and why it's null in our case.
Please consider this question from a Jenkins Multibranch perspective.
Our (git related) plugin installations is here [2] .
1 logging from Jenkins.
[Mon Jun 26 11:32:48 CEST 2017] Received Push event to branch BE-7394 in repository ServiceHouse/api UPDATED event from 172.18.0.1 ⇒ http://jenkins2.servicehouse.nl:8080/github-webhook/ with timestamp Mon Jun 26 11:32:43 CEST 2017
11:32:50 Connecting to https://api.github.com using shojenkinsuser/******
Looking up ServiceHouse/api
11:32:50 Connecting to https://api.github.com using shojenkinsuser/******
Looking up ServiceHouse/api
Getting remote branches...
Checking branch BE-7394
Getting remote branches...
Checking branch BE-7394
‘Jenkinsfile’ found
Met criteria
Changes detected: BE-7394 (01293286b6ee34056d8c92e21a6d39d18e537a81 → 35c16ef01bba5d27dd040a881cd3734fef271fd7)
Scheduled build for branch: BE-7394
0 branches were processed (query completed)
Done examining ServiceHouse/api
[2] Git related Installed plugins:

Answer 1

This variable sutup in the branch-api-plugin (setup source) and we have it working for pull requests or change requests.
For branches of the form -, it is not filled.
I can advise you to use:
BUILD_NUMBER
The current build number, such as "153"
BUILD_ID
The current build ID, identical to BUILD_NUMBER for builds created in
1.597+, but a YYYY-MM-DD_hh-mm-ss timestamp for older builds