diff --git a/steps/blsmooth.cwl b/steps/blsmooth.cwl
index e2fbdd1abc61caf81353b645d4d413f2de07e24d..9693c4aca2923175d6bf96e61c422bfe927eb103 100644
--- a/steps/blsmooth.cwl
+++ b/steps/blsmooth.cwl
@@ -22,9 +22,9 @@ inputs:
     type: boolean
     doc: 'If true performs smoothing'
     inputBinding:
-      prefix: -S=
+      prefix: -S
       valueFrom: "$(self ? 'True': 'False')"
-      separate: false
+      separate: true
 
   - default: 0.5
     id: bscalefactor