diff --git a/workflows/process_ddf.cwl b/workflows/process_ddf.cwl
index f05747bc8da3dd5e4991ca50c2638d6dd0f88130..da4be3ba2f86de557e949a57ee9da26218f83d62 100644
--- a/workflows/process_ddf.cwl
+++ b/workflows/process_ddf.cwl
@@ -116,6 +116,8 @@ steps:
         source: ncpu
       - id: chunkhours
         source: chunkhours
+      - id: do_subtraction
+        source: do_subtraction
     out:
       - id: regionbox
       - id: mslist