diff --git a/main/gradebook/lib/flatview_data_generator.class.php b/main/gradebook/lib/flatview_data_generator.class.php
index 40ae9686d2..2e1553cee3 100755
--- a/main/gradebook/lib/flatview_data_generator.class.php
+++ b/main/gradebook/lib/flatview_data_generator.class.php
@@ -314,10 +314,10 @@ class FlatViewDataGenerator
 	// Sort functions - used internally
 
 	function sort_by_last_name($item1, $item2) {
-		return api_strcmp($item1[1], $item2[1]);
+		return api_strcmp($item1[2], $item2[2]);
 	}
 
 	function sort_by_first_name($item1, $item2) {
-		return api_strcmp($item1[2], $item2[2]);
+		return api_strcmp($item1[3], $item2[3]);
 	}
 }