diff --git a/Jenkinsfile b/Jenkinsfile
index a8b47f3..74fc3ee 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -11,8 +11,7 @@ pipeline {
         stage('Build Docker Image') {
             steps {
                 script {
-                    def buildNumber = BUILD_NUMBER
-                    sh 'echo ${buildNumber}'
+                    sh 'echo ${env.BUILD_NUMBER}'
                     def dockerImage = docker.build('git.thisfro.ch/jenkinsci/pflaenzli', '-f Dockerfile . --tag git.thisfro.ch/jenkinsci/pflaenzli:${buildNumber}')
                 }
             }