diff --git a/js/jquery.tablesorter.js b/js/jquery.tablesorter.js
index ae0969682..7300e4678 100644
--- a/js/jquery.tablesorter.js
+++ b/js/jquery.tablesorter.js
@@ -2240,7 +2240,7 @@
 				cells = $rows[ i ].cells;
 				for ( j = 0; j < cells.length; j++ ) {
 					cell = cells[ j ];
-					rowIndex = cell.parentNode.rowIndex;
+					rowIndex = i;
 					rowSpan = cell.rowSpan || 1;
 					colSpan = cell.colSpan || 1;
 					if ( typeof matrix[ rowIndex ] === 'undefined' ) {