diff --git a/question/engine/datalib.php b/question/engine/datalib.php
index 175103d06df..beca1de177b 100644
--- a/question/engine/datalib.php
+++ b/question/engine/datalib.php
@@ -1279,22 +1279,21 @@ class question_file_saver implements question_response_files {
             $string .= $file->get_filepath() . $file->get_filename() . '|' .
                     $file->get_contenthash() . '|';
         }
-
-        if ($string) {
-            $hash = md5($string);
-        } else {
-            $hash = '';
-        }
+        $hash = md5($string);
 
         if (is_null($text)) {
-            return $hash;
+            if ($string) {
+                return $hash;
+            } else {
+                return '';
+            }
         }
 
         // We add the file hash so a simple string comparison will say if the
         // files have been changed. First strip off any existing file hash.
-        $text = preg_replace('/\s*<!-- File hash: \w+ -->\s*$/', '', $text);
-        $text = file_rewrite_urls_to_pluginfile($text, $draftitemid);
-        if ($hash) {
+        if ($text !== '') {
+            $text = preg_replace('/\s*<!-- File hash: \w+ -->\s*$/', '', $text);
+            $text = file_rewrite_urls_to_pluginfile($text, $draftitemid);
             $text .= '<!-- File hash: ' . $hash . ' -->';
         }
         return $text;
@@ -1391,8 +1390,15 @@ class question_file_loader implements question_response_files {
      */
     public function get_question_file_saver() {
 
-        // Value will be either a plain MD5 hash, or some real content, followed
-        // by an MD5 hash in a HTML comment. We only want the value in the latter case.
+        // There are three possibilities here for what $value will look like:
+        // 1) some HTML content followed by an MD5 hash in a HTML comment;
+        // 2) a plain MD5 hash;
+        // 3) or some real content, without any hash.
+        // The problem is that 3) is ambiguous in the case where a student writes
+        // a response that looks exactly like an MD5 hash. For attempts made now,
+        // we avoid case 3) by always going for case 1) or 2) (except when the
+        // response is blank. However, there may be case 3) data in the database
+        // so we need to handle it as best we can.
         if (preg_match('/\s*<!-- File hash: [0-9a-zA-Z]{32} -->\s*$/', $this->value)) {
             $value = preg_replace('/\s*<!-- File hash: [0-9a-zA-Z]{32} -->\s*$/', '', $this->value);
 
@@ -1400,8 +1406,7 @@ class question_file_loader implements question_response_files {
             $value = null;
 
         } else {
-            throw new coding_exception('$value passed to question_file_loader::get_question_file_saver' .
-                    ' was not of the expected form.');
+            $value = $this->value;
         }
 
         list($draftid, $text) = $this->step->prepare_response_files_draft_itemid_with_text(
diff --git a/question/type/essay/tests/walkthrough_test.php b/question/type/essay/tests/walkthrough_test.php
index fbc7a1ad811..e64149212cd 100644
--- a/question/type/essay/tests/walkthrough_test.php
+++ b/question/type/essay/tests/walkthrough_test.php
@@ -348,4 +348,77 @@ class qtype_essay_walkthrough_testcase extends qbehaviour_walkthrough_test_base
         $this->check_current_mark(null);
         $this->check_step_count(1);
     }
+
+    public function test_deferred_feedback_html_editor_with_files_attempt_on_last_no_files_uploaded() {
+        global $CFG, $USER;
+
+        $this->resetAfterTest(true);
+        $this->setAdminUser();
+        $usercontextid = context_user::instance($USER->id)->id;
+        $fs = get_file_storage();
+
+        // Create an essay question in the DB.
+        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');
+        $cat = $generator->create_question_category();
+        $question = $generator->create_question('essay', 'editorfilepicker', array('category' => $cat->id));
+
+        // Start attempt at the question.
+        $q = question_bank::load_question($question->id);
+        $this->start_attempt_at_question($q, 'deferredfeedback', 1);
+
+        $this->check_current_state(question_state::$todo);
+        $this->check_current_mark(null);
+        $this->check_step_count(1);
+
+        // Process a response and check the expected result.
+        // First we need to get the draft item ids.
+        $this->render();
+        if (!preg_match('/env=editor&amp;.*?itemid=(\d+)&amp;/', $this->currentoutput, $matches)) {
+            throw new coding_exception('Editor draft item id not found.');
+        }
+        $editordraftid = $matches[1];
+        if (!preg_match('/env=filemanager&amp;action=browse&amp;.*?itemid=(\d+)&amp;/', $this->currentoutput, $matches)) {
+            throw new coding_exception('File manager draft item id not found.');
+        }
+        $attachementsdraftid = $matches[1];
+
+        $this->process_submission(array(
+                'answer' => 'I refuse to draw you a picture, so there!',
+                'answerformat' => FORMAT_HTML,
+                'answer:itemid' => $editordraftid,
+                'attachments' => $attachementsdraftid));
+
+        $this->check_current_state(question_state::$complete);
+        $this->check_current_mark(null);
+        $this->check_step_count(2);
+        $this->save_quba();
+
+        // Now submit all and finish.
+        $this->finish();
+        $this->check_current_state(question_state::$needsgrading);
+        $this->check_current_mark(null);
+        $this->check_step_count(3);
+        $this->save_quba();
+
+        // Now start a new attempt based on the old one.
+        $this->load_quba();
+        $oldqa = $this->get_question_attempt();
+
+        $q = question_bank::load_question($question->id);
+        $this->quba = question_engine::make_questions_usage_by_activity('unit_test',
+                context_system::instance());
+        $this->quba->set_preferred_behaviour('deferredfeedback');
+        $this->slot = $this->quba->add_question($q, 1);
+        $this->quba->start_question_based_on($this->slot, $oldqa);
+
+        $this->check_current_state(question_state::$complete);
+        $this->check_current_mark(null);
+        $this->check_step_count(1);
+        $this->save_quba();
+
+        // Check the display.
+        $this->load_quba();
+        $this->render();
+        $this->assertRegExp('/I refuse to draw you a picture, so there!/', $this->currentoutput);
+    }
 }