diff --git a/preferences.php b/preferences.php
index 37b8128..8597fdd 100644
--- a/preferences.php
+++ b/preferences.php
@@ -93,7 +93,9 @@ switch ($att->pageparams->action) {
         foreach ($acronym as $id => $v) {
             $att->update_status($id, $acronym[$id], $description[$id], $grade[$id], null);
         }
-        att_update_all_users_grades($att->id, $att->course, $att->context, $cm);
+        if ($att->grade > 0) {
+            att_update_all_users_grades($att->id, $att->course, $att->context, $cm);
+        }
         break;
 }
 
diff --git a/sessions.php b/sessions.php
index b32e087..b03b3df 100644
--- a/sessions.php
+++ b/sessions.php
@@ -85,7 +85,9 @@ switch ($att->pageparams->action) {
 
         if (isset($confirm) && confirm_sesskey()) {
             $att->delete_sessions(array($sessionid));
-            att_update_all_users_grades($att->id, $att->course, $att->context, $cm);
+            if ($att->grade > 0) {
+                att_update_all_users_grades($att->id, $att->course, $att->context, $cm);
+            }
             redirect($att->url_manage(), get_string('sessiondeleted', 'attendance'));
         }
 
@@ -112,7 +114,9 @@ switch ($att->pageparams->action) {
             $sessionsids = explode('_', $sessionsids);
 
             $att->delete_sessions($sessionsids);
-            att_update_all_users_grades($att->id, $att->course, $att->context, $cm);
+            if ($att->grade > 0) {
+                att_update_all_users_grades($att->id, $att->course, $att->context, $cm);
+            }
             redirect($att->url_manage(), get_string('sessiondeleted', 'attendance'));
         }
         $sessid = required_param('sessid', PARAM_SEQUENCE);