diff --git a/tutorial/py.tornado/PythonServer.py b/tutorial/py.tornado/PythonServer.py
index 52932ff..7a34107 100755
--- a/tutorial/py.tornado/PythonServer.py
+++ b/tutorial/py.tornado/PythonServer.py
@@ -62,13 +62,13 @@
         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