diff --git a/sit b/sit
index c2d3ede..173d704 100755
--- a/sit
+++ b/sit
@@ -143,7 +143,12 @@ case $PLATFORM in
 esac
 echo "Loading modules: ${COMPILER_MODULE} ${MPI_MODULE}"
 
-module load ${COMPILER_MODULE} ${MPI_MODULE}
+if [ ! -z "$COMPILER_MODULE" ] ; then
+   module load ${COMPILER_MODULE}
+fi
+if [ ! -z "$MPI_MODULE" ] ; then
+   module load ${MPI_MODULE}
+fi
 
 if [ ! -z "${COMPILER}" ] ; then
     # reevaluate compiler version