Parallel computing with local jobs in RStudio

I have an R script which does some parallel execution within it using the snow and snowfall packages. If I run it as a local job in RStudio I get this error.

Warning message:
In searchCommandline(parallel, cpus = cpus, type = type, socketHosts = socketHosts,  :
  Unknown option on commandline: source('C:/Program Files/RStudio/R/modules/SourceWithProgress.R'); sourceWithProgress(script 

I guess because the rstudio jobs doesn't know how long it will take. My code still runs. But I would like to stop the error message appearing.

Any ideas?

Thanks, Jim Shady