diff --git a/demos/snow_package/snow-hello.R b/demos/snow_package/snow-hello.R
index fcda6bd..0a34de1 100644
--- a/demos/snow_package/snow-hello.R
+++ b/demos/snow_package/snow-hello.R
@@ -14,7 +14,7 @@ p <- rnorm(123, m = 33)
 
 ## Sub script asks for 18 cores, here cluster must
 ## be one smaller
-CLUSTERSIZE <- mpi.universe.size()-1
+CLUSTERSIZE <- Rmpi::mpi.universe.size()-1
 
 cl <- makeCluster(CLUSTERSIZE, type = "MPI")