SQL Server Replication Agent Profile -Output Parameter

I'm trying to add the -Output parameter to my log reader agent for transactional replication and getting this error:

Msg 21805, Level 16, State 1, Procedure sp_MSvalidate_agent_parameter, Line 92
The agent profile creation process cannot validate the specified agent parameter value.
'K:\Inst06_TempDB\MSSQL10.INST06\MSSQL\Log\ReplOutput-LogReaderAgent.txt' is not a valid
value for the '-Output' parameter. The value must be an integer. Verify that replication
is installed properly and that sp_add_agent_parameter is invoked with a valid value.

http://msdn.microsoft.com/en-us/library/ms146878(v=SQL.100).aspx shows that -Output expects a path, not an integer as the error message says.

Pub & Sub are both v9.0.4211, Dist is v10.0.2723

My Script (run at distributor):

EXEC sp_change_agent_parameter @profile_id = 18
                              ,@parameter_name = '-Output'
                              ,@parameter_value = 'K:\Inst06_TempDB\MSSQL10.INST06\MSSQL\Log\ReplOutput-LogReaderAgent.txt'
EXEC sp_change_agent_parameter @profile_id = 18
                              ,@parameter_name = '-OutputVerboseLevel'
                              ,@parameter_value = '2' --[0|1|2|3|4] default 2