diff --git a/src/fvOptions/cellSetOption/cellSetOption.H b/src/fvOptions/cellSetOption/cellSetOption.H
index aa020ef849..e45c5adce7 100644
--- a/src/fvOptions/cellSetOption/cellSetOption.H
+++ b/src/fvOptions/cellSetOption/cellSetOption.H
@@ -122,6 +122,7 @@ Usage
       points    | Use cells containing a given set of points
       movingPoints | Use cells containing a given set of moving points
       geometric | Select cells based on topoSetCellSource actions
+      cellType  | For overset only : use cells of type 'porous
     \endverbatim
 
     The inherited entries are elaborated in: