diff --git a/src/usr/local/bin/validate_workflow.sh b/src/usr/local/bin/validate_workflow.sh
index 910db0fe7b91730c42aa1145fd384ed290b6386f..d866ba3eb45484ed6f61b3b28eb7a8e949265d7b 100755
--- a/src/usr/local/bin/validate_workflow.sh
+++ b/src/usr/local/bin/validate_workflow.sh
@@ -325,7 +325,7 @@ get_cli_args() {
             || [[ -n "${VALID_FOLDER}" ]] \
             || [[ -n "${INVALID_FOLDER}" ]] \
             || [[ "${FILES_MODE}" = "sort" ]] \
-            || [[ -n "${SINGLE_FILE}" ]] \
+            || [[ "${SINGLE_FILE}" -eq 1 ]] \
             ; then 
             error "param --pipe not combinable with params --daemon, --result-folder, --watch-folder, --valid-folder, --invalid-folder, --files-mode"
             exit 1