diff --git a/add_form.php b/add_form.php
index d69dfa0..cfbaa87 100644
--- a/add_form.php
+++ b/add_form.php
@@ -118,7 +118,8 @@ class mod_attendance_add_form extends moodleform {
         }
 
         // Students can mark own attendance.
-        if (!empty(get_config('attendance', 'studentscanmark'))) {
+        $configcanmark = get_config('attendance', 'studentscanmark');
+        if (!empty($configcanmark)) {
             $mform->addElement('checkbox', 'studentscanmark', '', get_string('studentscanmark', 'attendance'));
             $mform->addHelpButton('studentscanmark', 'studentscanmark', 'attendance');
         } else {
diff --git a/renderer.php b/renderer.php
index 0f16f98..1c57c04 100644
--- a/renderer.php
+++ b/renderer.php
@@ -813,7 +813,8 @@ class mod_attendance_renderer extends plugin_renderer_base {
                 $cell->colspan = 2;
                 $row->cells[] = $cell;
             } else {
-                if (!empty(get_config('attendance', 'studentscanmark')) && !empty($sess->studentscanmark)) {
+                $configjs = get_config('attendance', 'studentscanmark');
+                if (!empty($configjs) && !empty($sess->studentscanmark)) {
                     // Student can mark their own attendance.
                     // URL to the page that lets the student modify their attendance.
                     $url = new moodle_url('/mod/attendance/attendance.php',
diff --git a/sessions.php b/sessions.php
index 164b193..ff4fd4b 100644
--- a/sessions.php
+++ b/sessions.php
@@ -234,7 +234,8 @@ function construct_sessions_data_for_add($formdata) {
     $duration = $sesendtime - $sesstarttime;
     $now = time();
 
-    if (empty(get_config('attendance', 'studentscanmark'))) {
+    $configcanmark = get_config('attendance', 'studentscanmark');
+    if (empty($configcanmark)) {
         $formdata->studentscanmark = 0;
     }