diff --git a/workflows/prefactor_calibrator.cwl b/workflows/prefactor_calibrator.cwl
index c602ee942658f8b6a7a0ad02dc6fe2ac9b10440c..a3bf0707053a344eebc44341b976e5284cb99711 100644
--- a/workflows/prefactor_calibrator.cwl
+++ b/workflows/prefactor_calibrator.cwl
@@ -281,6 +281,7 @@ steps:
     label: prep
     scatter:
       - msin
+    scatterMethod: flat_crossproduct
     'sbg:x': 0
     'sbg:y': 0
 requirements: