diff --git a/se/sics/mspsim/ui/SerialMon.java b/se/sics/mspsim/ui/SerialMon.java
index 8526aa1..8c5796b 100644
--- a/se/sics/mspsim/ui/SerialMon.java
+++ b/se/sics/mspsim/ui/SerialMon.java
@@ -98,7 +98,6 @@ public class SerialMon implements KeyListener, USARTListener,
 
     usart.addStateChangeListener(this);
     textArea.addKeyListener(this);
-    usart.addStateChangeListener(this);
   }
 
   public void saveWindowBounds() {