diff --git a/direct/src/showbase/Pool.py b/direct/src/showbase/Pool.py
index 5631635249..fb802f594c 100755
--- a/direct/src/showbase/Pool.py
+++ b/direct/src/showbase/Pool.py
@@ -21,8 +21,11 @@ class Pool:
 
     notify = DirectNotifyGlobal.directNotify.newCategory("Pool")
     
-    def __init__(self, free=[]):
-        self.__free = free
+    def __init__(self, free=None):
+        if free:
+            self.__free = free
+        else:
+            self.__free = []
         self.__used = []
 
     def add(self, item):