diff --git a/src/immersedBoundary/immersedBoundary/immersedBoundaryFvPatch/immersedBoundaryFvPatch.C b/src/immersedBoundary/immersedBoundary/immersedBoundaryFvPatch/immersedBoundaryFvPatch.C
index 0c47673c7..831c1436d 100644
--- a/src/immersedBoundary/immersedBoundary/immersedBoundaryFvPatch/immersedBoundaryFvPatch.C
+++ b/src/immersedBoundary/immersedBoundary/immersedBoundaryFvPatch/immersedBoundaryFvPatch.C
@@ -356,6 +356,7 @@ Foam::tmp<Foam::vectorField> Foam::immersedBoundaryFvPatch::nf() const
 
 Foam::tmp<Foam::vectorField> Foam::immersedBoundaryFvPatch::delta() const
 {
+    // Not strictly needed: this is for debug only.  HJ, 5/Apr/2019
     return ibPolyPatch_.ibPatch().faceCentres() - Cn();
 }