diff --git a/layouts/rowcol.go b/layouts/rowcol.go
index cdb60aa..d195dae 100644
--- a/layouts/rowcol.go
+++ b/layouts/rowcol.go
@@ -57,6 +57,7 @@ func (column Column) Arrange (hints tomo.LayoutHints, boxes []tomo.Box) {
 				freeSpace -= float64(box.MinimumSize().X)
 			}
 		}
+		expandingSize = freeSpace / float64(nExpanding)
 	}
 
 	// determine width