diff --git a/src/run-policy/run-mmpol.sh b/src/run-policy/run-mmpol.sh
index 13cd12bb54f9e236f5048a2b1b5f999667782b52..700f0f001e8fa36b6f2e0ad724446c65b0278421 100755
--- a/src/run-policy/run-mmpol.sh
+++ b/src/run-policy/run-mmpol.sh
@@ -96,10 +96,10 @@ if [[ -z "${output_log_prefix}" ]]; then
 fi
 
 # create temporary working directory for list aggregation
-tmpglobal=${outdir}/slurm-tmp-${SLURM_JOBID}
-tmpscratch=${outdir}/slurm-tmp-${SLURM_JOBID}
+tmpglobal="${outdir}/slurm-tmp-${SLURM_JOBID}"
+tmpscratch="${outdir}/slurm-tmp-${SLURM_JOBID}"
 
-nodes=`scontrol show hostnames "${SLURM_JOB_NODELIST}" | tr '\n' ',' | sed -e 's/,$//'`
+nodes=$(scontrol show hostnames "${SLURM_JOB_NODELIST}" | tr '\n' ',' | sed -e 's/,$//')
 cores="${SLURM_CPUS_PER_TASK}"
 
 DATESTR=$(date +'%Y%m%dT%H%M%S')