diff --git a/hmftools.wdl b/hmftools.wdl
index 1e25938db0eaa5a44b068d733c6eb8173a6b1d5b..199d7d88130a3eb8b4f9a9ad3925436296a3e142 100644
--- a/hmftools.wdl
+++ b/hmftools.wdl
@@ -577,7 +577,7 @@ task Protect {
         -ref_genome_version ~{refGenomeVersion} \
         -tumor_sample_id ~{tumorName} \
         -reference_sample_id ~{normalName} \
-        -primary_tumor_doids ~{sep=";" sampleDoids} \
+        -primary_tumor_doids '~{sep=";" sampleDoids}' \
         -output_dir ~{outputDir} \
         -serve_actionability_dir ~{sub(serveActionability[0], basename(serveActionability[0]), "")} \
         -doid_json ~{doidsJson} \