diff --git a/Jenkinsfile b/Jenkinsfile
index 82142d8..5119a1b 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -41,7 +41,8 @@
                 sh 'mkdir -p ${WORKSPACE}/.m2'
                 sh 'docker logout'   // needed because sometimes cached credentials break the following step (creds aren't needed)
                 echo 'Building docker image for test environment ...'
-                environmentDockerImage = docker.build('brooklyn:${DOCKER_TAG}')
+                echo "Using docker tag DOCKER_TAG=${DOCKER_TAG}" // double quotes to resolve env vars
+                environmentDockerImage = docker.build("brooklyn:${DOCKER_TAG}") // double quotes to resolve env vars
             }
 
             stage('Run tests') {