diff --git a/direct/src/showbase/ContainerLeakDetector.py b/direct/src/showbase/ContainerLeakDetector.py
index 714c02283e..f2c5ad645b 100755
--- a/direct/src/showbase/ContainerLeakDetector.py
+++ b/direct/src/showbase/ContainerLeakDetector.py
@@ -10,6 +10,8 @@ import types
 import weakref
 import random
 import builtins
+import sys
+
 
 deadEndTypes = frozenset((
     types.BuiltinFunctionType, types.BuiltinMethodType,