diff --git a/workflow/psrfits_requantisation.cwl b/workflow/psrfits_requantisation.cwl
index 602c67926e0e7dee67daa950a088f454bddad51a..ca8bbd1e9f12b70b7040123aefbb2102db9ab0ae 100644
--- a/workflow/psrfits_requantisation.cwl
+++ b/workflow/psrfits_requantisation.cwl
@@ -18,7 +18,7 @@ outputs:
     type: Any
     outputSource: requantise/summary
   - id: summary_file
-    type: File
+    type: File?
     outputSource: requantise/file_content
 
 steps: