diff --git a/code-ch13/op.py b/code-ch13/op.py
index 4e9e3831..e675c889 100644
--- a/code-ch13/op.py
+++ b/code-ch13/op.py
@@ -285,7 +285,7 @@ def op_2over(stack):
 def op_2rot(stack):
     if len(stack) < 6:
         return False
-    stack.extend(stack[-6:-4])
+    stack[-6:] = stack[-4:] + stack[-6:-4]
     return True