diff --git a/extras/src/main/java/edu/umd/cs/piccolox/event/PNotificationCenter.java b/extras/src/main/java/edu/umd/cs/piccolox/event/PNotificationCenter.java
index c1c96a9..8272e7f 100644
--- a/extras/src/main/java/edu/umd/cs/piccolox/event/PNotificationCenter.java
+++ b/extras/src/main/java/edu/umd/cs/piccolox/event/PNotificationCenter.java
@@ -79,7 +79,7 @@
      * 
      * @return singleton instance of PNotificationCenter
      */
-    public static PNotificationCenter defaultCenter() {
+    public synchronized static PNotificationCenter defaultCenter() {
         if (DEFAULT_CENTER == null) {
             DEFAULT_CENTER = new PNotificationCenter();
         }