Rcpp sourceCpp with parallel foreach

I have a function foo written in Rcpp that I can use in my R session via sourceCpp.

I also have a cluster of machines using R parallel makePSOCKCluster. I want to run a parallel foreach loop through these machines that will use foo. I can see that the function is exported via foreach, but I think that only the Rcpp function pointer is exported. How can I make sure that the foo function itself is also exported?