diff --git a/tests/API-dhcp/Jenkinsfile b/tests/API-dhcp/Jenkinsfile
index 1c3d6cf..b5ae181 100644
--- a/tests/API-dhcp/Jenkinsfile
+++ b/tests/API-dhcp/Jenkinsfile
@@ -112,6 +112,10 @@ pipeline {
 
 @NonCPS
 def getUserEmail(userId) {
-    def user = jenkins.model.Jenkins.instance.getUser(userId)
-    return user.getProperty(jenkins.plugins.mailer.tasks.Mailer.UserProperty)?.getAddress()
+    def jenkinsInstance = jenkins.model.Jenkins.getInstanceOrNull()
+    if (jenkinsInstance != null) {
+        def user = jenkinsInstance.getUser(userId)
+        return user.getProperty(jenkins.plugins.mailer.tasks.Mailer.UserProperty)?.getAddress()
+    }
+    return null
 }