diff --git a/src/main/java/de/ailis/usb4java/support/EventListenerList.java b/src/main/java/de/ailis/usb4java/support/EventListenerList.java
index 352d798..a2e6fb1 100644
--- a/src/main/java/de/ailis/usb4java/support/EventListenerList.java
+++ b/src/main/java/de/ailis/usb4java/support/EventListenerList.java
@@ -31,6 +31,7 @@ public abstract class EventListenerList<T extends EventListener>
      */
     public final void add(final T listener)
     {
+        if (this.listeners.contains(listener)) return;
         this.listeners.add(listener);
     }