diff --git a/src/main/java/jpo/sdw/depositor/DepositorProperties.java b/src/main/java/jpo/sdw/depositor/DepositorProperties.java
index 5e9d060..f657948 100644
--- a/src/main/java/jpo/sdw/depositor/DepositorProperties.java
+++ b/src/main/java/jpo/sdw/depositor/DepositorProperties.java
@@ -68,11 +68,12 @@ void initialize() {
       if (getSubscriptionTopics() == null || getSubscriptionTopics().length == 0) {
          // get environment variable SDW_SUBSCRIPTION_TOPIC
          String topics = System.getenv("SDW_SUBSCRIPTION_TOPIC");
-         subscriptionTopics = topics.split(",");
          if (topics == null || topics.isEmpty()) {
             topics = String.join(",", DEFAULT_SUBSCRIPTION_TOPICS);
             logger.info("No Kafka subscription topics specified in configuration, defaulting to {}", topics);
             subscriptionTopics = DEFAULT_SUBSCRIPTION_TOPICS;
+         } else {
+            subscriptionTopics = topics.split(",");
          }
       }