diff --git a/mod/assign/locallib.php b/mod/assign/locallib.php
index 6d80290191767..bf618e8c83926 100644
--- a/mod/assign/locallib.php
+++ b/mod/assign/locallib.php
@@ -1022,6 +1022,8 @@ public function display_grade($grade, $editing, $userid=0, $modified=0) {
 
         static $scalegrades = array();
 
+        $o = '';
+
         if ($this->get_instance()->grade >= 0) {
             // Normal number
             if ($editing && $this->get_instance()->grade > 0) {
@@ -1030,17 +1032,20 @@ public function display_grade($grade, $editing, $userid=0, $modified=0) {
                 } else {
                     $displaygrade = format_float($grade);
                 }
-                $o = '<label class="accesshide" for="quickgrade_' . $userid . '">' . get_string('usergrade', 'assign') . '</label>';
-                $o .= '<input type="text" id="quickgrade_' . $userid . '" name="quickgrade_' . $userid . '" value="' . $displaygrade
-                        . '" size="6" maxlength="10" class="quickgrade"/>';
+                $o .= '<label class="accesshide" for="quickgrade_' . $userid . '">' . get_string('usergrade', 'assign') . '</label>';
+                $o .= '<input type="text" id="quickgrade_' . $userid . '" name="quickgrade_' . $userid . '" value="' . 
+                      $displaygrade . '" size="6" maxlength="10" class="quickgrade"/>';
                 $o .= '&nbsp;/&nbsp;' . format_float($this->get_instance()->grade,2);
                 $o .= '<input type="hidden" name="grademodified_' . $userid . '" value="' . $modified . '"/>';
                 return $o;
             } else {
+                $o .= '<input type="hidden" name="grademodified_' . $userid . '" value="' . $modified . '"/>';
                 if ($grade == -1 || $grade === null) {
-                    return '-';
+                    $o .= '-';
+                    return $o;
                 } else {
-                    return format_float(($grade),2) .'&nbsp;/&nbsp;'. format_float($this->get_instance()->grade,2);
+                    $o .= format_float(($grade),2) .'&nbsp;/&nbsp;'. format_float($this->get_instance()->grade,2);
+                    return $o;
                 }
             }
 
@@ -1050,11 +1055,12 @@ public function display_grade($grade, $editing, $userid=0, $modified=0) {
                 if ($scale = $DB->get_record('scale', array('id'=>-($this->get_instance()->grade)))) {
                     $this->cache['scale'] = make_menu_from_list($scale->scale);
                 } else {
-                    return '-';
+                    $o .= '-';
+                    return $o;
                 }
             }
             if ($editing) {
-                $o = '<label class="accesshide" for="quickgrade_' . $userid . '">' . get_string('usergrade', 'assign') . '</label>';
+                $o .= '<label class="accesshide" for="quickgrade_' . $userid . '">' . get_string('usergrade', 'assign') . '</label>';
                 $o .= '<select name="quickgrade_' . $userid . '" class="quickgrade">';
                 $o .= '<option value="-1">' . get_string('nograde') . '</option>';
                 foreach ($this->cache['scale'] as $optionid => $option) {
@@ -1070,9 +1076,11 @@ public function display_grade($grade, $editing, $userid=0, $modified=0) {
             } else {
                 $scaleid = (int)$grade;
                 if (isset($this->cache['scale'][$scaleid])) {
-                    return $this->cache['scale'][$scaleid];
+                    $o .= $this->cache['scale'][$scaleid];
+                    return $o;
                 }
-                return '-';
+                $o .= '-';
+                return $o;
             }
         }
     }
@@ -3448,12 +3456,12 @@ private function process_save_quick_grades() {
         // gets a list of possible users and look for values based upon that.
         foreach ($participants as $userid => $unused) {
             $modified = optional_param('grademodified_' . $userid, -1, PARAM_INT);
-            // gather the userid, updated grade and last modified value
+            // Gather the userid, updated grade and last modified value.
             $record = new stdClass();
             $record->userid = $userid;
             $gradevalue = optional_param('quickgrade_' . $userid, '', PARAM_TEXT);
             if($modified >= 0) {
-                $record->grade = unformat_float(required_param('quickgrade_' . $record->userid, PARAM_TEXT));
+                $record->grade = unformat_float(optional_param('quickgrade_' . $record->userid, -1, PARAM_TEXT));
             }
             $record->lastmodified = $modified;
             $record->gradinginfo = grade_get_grades($this->get_course()->id, 'mod', 'assign', $this->get_instance()->id, array($userid));
@@ -3491,8 +3499,7 @@ private function process_save_quick_grades() {
             foreach ($this->feedbackplugins as $plugin) {
                 if ($plugin->is_visible() && $plugin->is_enabled() && $plugin->supports_quickgrading()) {
                     if ($plugin->is_quickgrading_modified($modified->userid, $grade)) {
-                        if ($modified->lastmodified >= 0 &&
-                            (int)$current->lastmodified > (int)$modified->lastmodified) {
+                        if ((int)$current->lastmodified > (int)$modified->lastmodified) {
                             return get_string('errorrecordmodified', 'assign');
                         } else {
                             $modifiedusers[$modified->userid] = $modified;