diff --git a/vaadin-grid-table-row.html b/vaadin-grid-table-row.html
index 69960813b..3d3c79492 100644
--- a/vaadin-grid-table-row.html
+++ b/vaadin-grid-table-row.html
@@ -99,20 +99,21 @@
       },
 
       _updateCells: function() {
-        // columns > cells means that there is an extra col for multiselection
-        var multiSel = this.columns.length > this.cells.length ? 1 : 0;
+        // Extra columns are used for multi-selection or hierarchy.
+        var extraColumns = this.columns.length > this.cells.length ? 1 : 0;
 
         for (var i = 0, l = this.cells.length, colspan; i < l; i += colspan) {
           var cell = this.cells[i];
           colspan = cell.colspan || 1;
-          var width = this.columns[i + multiSel].width;
-          var flex = this.columns[i + multiSel].flex;
+          var width = this.columns[i + extraColumns].width;
+          var flex = this.columns[i + extraColumns].flex;
 
-          // Visit colspanned cells to hide then and increase width and flex of parent
+          // Visit colspanned cells to hide them, and increase parent width and flex.
           for (var j = 1; j < colspan && i + j < l; j++) {
             this.cells[i + j].style.display = 'none';
-            width = width + ' + ' + this.columns[i + multiSel + j].width;
-            flex += this.columns[i + multiSel + j].flex;
+
+            width = width + ' + ' + this.columns[i + extraColumns + j].width;
+            flex += this.columns[i + extraColumns + j].flex;
           }
 
           cell.style.flexBasis = 'calc(' + width + ')';