diff --git a/steps/concatenate_files.cwl b/steps/concatenate_files.cwl
index ba9c5f64a2fdd2b807f514ea03b2face9c45cfe3..e3f5bdac0a5e03c744726b23699baf0c3834a212 100644
--- a/steps/concatenate_files.cwl
+++ b/steps/concatenate_files.cwl
@@ -32,6 +32,6 @@ requirements:
           FILE_LIST=("\${@}")
           FILE_PREFIX=$(inputs.file_prefix)
           FILE_SUFFIX=$(inputs.file_suffix === null ? '' : inputs.file_suffix)
-          cat "\${FILE_LIST[@]}" > "\$FILE_PREFIX.\$FILE_SUFFIX"
+          cat "\${FILE_LIST[@]}" > $FILE_PREFIX.$FILE_SUFFIX
         writable: false
   - class: InlineJavascriptRequirement