diff --git a/util/src/test/java/com/ning/billing/util/notificationq/MockNotificationQueueService.java b/util/src/test/java/com/ning/billing/util/notificationq/MockNotificationQueueService.java
index 1ae3a5c..6550c4c 100644
--- a/util/src/test/java/com/ning/billing/util/notificationq/MockNotificationQueueService.java
+++ b/util/src/test/java/com/ning/billing/util/notificationq/MockNotificationQueueService.java
@@ -43,9 +43,10 @@ public class MockNotificationQueueService extends NotificationQueueServiceBase {
public int doProcessEvents() {
int result = 0;
-
- for (NotificationQueue cur : queues.values()) {
- result += doProcessEventsForQueue((MockNotificationQueue) cur);
+ synchronized (queues) {
+ for (NotificationQueue cur : queues.values()) {
+ result += doProcessEventsForQueue((MockNotificationQueue) cur);
+ }
}
return result;
}