diff --git a/OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs b/OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs
index c71594916c..c4b025a299 100644
--- a/OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs
+++ b/OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs
@@ -8466,7 +8466,10 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         {
             lock (m_clientInterfaces)
             {
-                m_clientInterfaces.Add(typeof(T), iface);
+                if (!m_clientInterfaces.ContainsKey(typeof(T)))
+                {
+                    m_clientInterfaces.Add(typeof(T), iface);
+                }
             }
         }