Fix is in https://github.com/jenkinsci/copyartifact-plugin/pull/6

Code changed in jenkins
User: Fred G
Path:
src/main/java/hudson/plugins/copyartifact/TriggeredBuildSelector.java
src/test/java/hudson/plugins/copyartifact/CopyArtifactTest.java
http://jenkins-ci.org/commit/copyartifact-plugin/781095924528496b3ec7998a625808875c5215c0
Log:
Reverted imports to original style, adapted test for JENKINS-11828

Code changed in jenkins
User: Fred G
Path:
src/main/java/hudson/plugins/copyartifact/CopyArtifact.java
src/main/java/hudson/plugins/copyartifact/FilePathCopyMethod.java
src/main/java/hudson/plugins/copyartifact/TriggeredBuildSelector.java
src/test/java/hudson/plugins/copyartifact/CopyArtifactTest.java
http://jenkins-ci.org/commit/copyartifact-plugin/4fb9dba52c63c433cd44403af71067c79f2764e5
Log:
Merge pull request #7 from fredg02/master

merged tivv's pull request and adapted test for JENKINS-11828

Compare: https://github.com/jenkinsci/copyartifact-plugin/compare/6ff97e6...4fb9dba

Integrated in plugins_copyartifact #69
Reverted imports to original style, adapted test for JENKINS-11828

Fred G : 781095924528496b3ec7998a625808875c5215c0
Files :

• src/main/java/hudson/plugins/copyartifact/TriggeredBuildSelector.java
• src/test/java/hudson/plugins/copyartifact/CopyArtifactTest.java

Fixed in version 1.19. Thanks Vitalii.

I wonder how to utilised this in Declarative Pipeline. 
I have something like this:

stage('Copy Artifacts from the UPSTREAM job') {
      steps {
         script {
             step ([$class: 'CopyArtifact',
             projectName: 'Avon Trunk Boot Verify',
             selector: upstream(),
             filter: "FW/mcspuck*.*,FW/mcsangelo*.*",
             target: '.']);
         }
      }
    }

But dunno how to set that attribute to true like it is in the UI.

Thanks