diff --git a/tutorial/py.twisted/PythonServer.py b/tutorial/py.twisted/PythonServer.py
index f023cac..227f6d4 100755
--- a/tutorial/py.twisted/PythonServer.py
+++ b/tutorial/py.twisted/PythonServer.py
@@ -59,13 +59,13 @@
     elif work.op == Operation.DIVIDE:
       if work.num2 == 0:
         x = InvalidOperation()
-        x.what = work.op
+        x.whatOp = work.op
         x.why = 'Cannot divide by 0'
         raise x
       val = work.num1 / work.num2
     else:
       x = InvalidOperation()
-      x.what = work.op
+      x.whatOp = work.op
       x.why = 'Invalid operation'
       raise x