diff --git a/mosgi.managedelements.osgiprobes.tab/src/main/java/org/apache/felix/mosgi/managedelements/osgiprobes/tab/OsgiProbesTabUI.java b/mosgi.managedelements.osgiprobes.tab/src/main/java/org/apache/felix/mosgi/managedelements/osgiprobes/tab/OsgiProbesTabUI.java
index c5c7ea7..2e315f7 100644
--- a/mosgi.managedelements.osgiprobes.tab/src/main/java/org/apache/felix/mosgi/managedelements/osgiprobes/tab/OsgiProbesTabUI.java
+++ b/mosgi.managedelements.osgiprobes.tab/src/main/java/org/apache/felix/mosgi/managedelements/osgiprobes/tab/OsgiProbesTabUI.java
@@ -68,10 +68,14 @@
   //////////////////////////////////////////
   public void registerServicePlugin(){
     sreg = m_context.registerService(Plugin.class.getName(), this, null);
+    
   }
   
   public void unregisterServicePlugin(){
-    sreg.unregister();   
+    if (sreg!=null){
+      sreg.unregister();   
+      sreg=null;
+    }
   }
   
   public String pluginLocation(){