--- a/Graphics/PackageItem.py	Wed Mar 22 18:45:15 2017 +0100
+++ b/Graphics/PackageItem.py	Wed Mar 22 18:50:20 2017 +0100
@@ -21,7 +21,7 @@
     """
     Class implementing the package model.
     """
-    def __init__(self, name, moduleslist=[]):
+    def __init__(self, name, moduleslist=None):
         """
         Constructor
         
@@ -30,7 +30,7 @@
         """
         super(PackageModel, self).__init__(name)
         
-        self.moduleslist = moduleslist
+        self.moduleslist = [] if moduleslist is None else moduleslist[:]
     
     def addModule(self, modulename):
         """