diff --git a/steps/DP3.AveragerStepGenerator.cwl b/steps/DP3.AveragerStepGenerator.cwl
index 3244559446e2e0347df72366941cf7e3d5fe97c9..836d6eb5ee3f5e7476249e98038bcd33269622d9 100755
--- a/steps/DP3.AveragerStepGenerator.cwl
+++ b/steps/DP3.AveragerStepGenerator.cwl
@@ -7,6 +7,7 @@ id: average_step_generator
 inputs:
   - id: input_parset
     type: Any[]?
+    default: []
   - id: step_name
     type: string
     doc: unique name for the step