diff --git a/workflows/linc_target/selfcal_targ_hba.cwl b/workflows/linc_target/selfcal_targ_hba.cwl
index 5852dbd01af9701e5adda125cabd453afb357ac6..b7f4a280ccf4a74d4ddcbefd12e1a7e371d6badd 100644
--- a/workflows/linc_target/selfcal_targ_hba.cwl
+++ b/workflows/linc_target/selfcal_targ_hba.cwl
@@ -16,7 +16,7 @@ inputs:
     type: string?
     default: 'phaseonly'
   - id: selfcal_hba_imsize
-    type: int[]
+    type: int[]?
     default: [20000,20000]
   - id: wsclean_tmpdir
     type: string