Index: lams_gradebook/src/java/org/lamsfoundation/lams/gradebook/service/GradebookService.java
===================================================================
diff -u -ra18dc17749e22a33ea027d5cdea75369d5e40743 -r9c45f8415c6c06df681a4e94205aa71d123b0bfa
--- lams_gradebook/src/java/org/lamsfoundation/lams/gradebook/service/GradebookService.java	(.../GradebookService.java)	(revision a18dc17749e22a33ea027d5cdea75369d5e40743)
+++ lams_gradebook/src/java/org/lamsfoundation/lams/gradebook/service/GradebookService.java	(.../GradebookService.java)	(revision 9c45f8415c6c06df681a4e94205aa71d123b0bfa)
@@ -1195,7 +1195,7 @@
 	    userDataRow.addCell(userRow.getTimeTakenSeconds());
 	    Double mark = userRow.getMark();
 	    if (isWeighted) {
-		userDataRow.addPercentageCell(mark / 100.0);
+		userDataRow.addPercentageCell(mark == null ? 0 : mark / 100.0);
 	    } else {
 		userDataRow.addCell(mark);
 	    }