diff --git a/course/moodleform_mod.php b/course/moodleform_mod.php
index 29e0d03935e..66b3d9f3e12 100644
--- a/course/moodleform_mod.php
+++ b/course/moodleform_mod.php
@@ -224,8 +224,10 @@ abstract class moodleform_mod extends moodleform {
                 // is changed, maybe someone has completed it now)
                 $mform->getElement('completionunlocked')->setValue(1);
             } else {
-                // Has the element been unlocked?
-                if ($mform->exportValue('unlockcompletion')) {
+                // Has the element been unlocked, either by the button being pressed
+                // in this request, or the field already being set from a previous one?
+                if ($mform->exportValue('unlockcompletion') ||
+                        $mform->exportValue('completionunlocked')) {
                     // Yes, add in warning text and set the hidden variable
                     $mform->insertElementBefore(
                         $mform->createElement('static', 'completedunlocked',