diff --git a/lib/filestorage/file_storage.php b/lib/filestorage/file_storage.php
index c832f619057..e4ba86e5434 100644
--- a/lib/filestorage/file_storage.php
+++ b/lib/filestorage/file_storage.php
@@ -2154,7 +2154,7 @@ class file_storage {
         $now = time();
         foreach ($rs as $record) {
             $this->update_references($record->id, $now, null,
-                    $storedfile->get_contenthash(), $storedfile->get_filesize(), 0);
+                    $storedfile->get_contenthash(), $storedfile->get_filesize(), 0, $storedfile->get_timemodified());
         }
         $rs->close();
     }
@@ -2372,8 +2372,9 @@ class file_storage {
      * @param string $contenthash
      * @param int $filesize
      * @param int $status 0 if ok or 666 if source is missing
+     * @param int $timemodified last time modified of the source, if known
      */
-    public function update_references($referencefileid, $lastsync, $lifetime, $contenthash, $filesize, $status) {
+    public function update_references($referencefileid, $lastsync, $lifetime, $contenthash, $filesize, $status, $timemodified = null) {
         global $DB;
         $referencefileid = clean_param($referencefileid, PARAM_INT);
         $lastsync = clean_param($lastsync, PARAM_INT);
@@ -2383,9 +2384,10 @@ class file_storage {
         $params = array('contenthash' => $contenthash,
                     'filesize' => $filesize,
                     'status' => $status,
-                    'referencefileid' => $referencefileid);
+                    'referencefileid' => $referencefileid,
+                    'timemodified' => $timemodified);
         $DB->execute('UPDATE {files} SET contenthash = :contenthash, filesize = :filesize,
-            status = :status
+            status = :status ' . ($timemodified ? ', timemodified = :timemodified' : '') . '
             WHERE referencefileid = :referencefileid', $params);
         $data = array('id' => $referencefileid, 'lastsync' => $lastsync);
         $DB->update_record('files_reference', (object)$data);
diff --git a/lib/filestorage/stored_file.php b/lib/filestorage/stored_file.php
index a959baf7053..b115f965673 100644
--- a/lib/filestorage/stored_file.php
+++ b/lib/filestorage/stored_file.php
@@ -961,8 +961,9 @@ class stored_file {
      * @param null|string $contenthash if set to null contenthash is not changed
      * @param int $filesize new size of the file
      * @param int $status new status of the file (0 means OK, 666 - source missing)
+     * @param int $timemodified last time modified of the source, if known
      */
-    public function set_synchronized($contenthash, $filesize, $status = 0) {
+    public function set_synchronized($contenthash, $filesize, $status = 0, $timemodified = null) {
         if (!$this->is_external_file()) {
             return;
         }
@@ -974,12 +975,15 @@ class stored_file {
             $oldcontenthash = $this->file_record->contenthash;
         }
         // this will update all entries in {files} that have the same filereference id
-        $this->fs->update_references($this->file_record->referencefileid, $now, null, $contenthash, $filesize, $status);
+        $this->fs->update_references($this->file_record->referencefileid, $now, null, $contenthash, $filesize, $status, $timemodified);
         // we don't need to call update() for this object, just set the values of changed fields
         $this->file_record->contenthash = $contenthash;
         $this->file_record->filesize = $filesize;
         $this->file_record->status = $status;
         $this->file_record->referencelastsync = $now;
+        if ($timemodified) {
+            $this->file_record->timemodified = $timemodified;
+        }
         if (isset($oldcontenthash)) {
             $this->fs->deleted_file_cleanup($oldcontenthash);
         }
diff --git a/repository/filesystem/lib.php b/repository/filesystem/lib.php
index 1585d883ac5..5ce146166d6 100644
--- a/repository/filesystem/lib.php
+++ b/repository/filesystem/lib.php
@@ -375,7 +375,8 @@ class repository_filesystem extends repository {
                 $filesize = filesize($filepath);
             }
             $issyncing = false;
-            $file->set_synchronized($contenthash, $filesize);
+            $modified = filemtime($filepath);
+            $file->set_synchronized($contenthash, $filesize, 0, $modified);
         } else {
             $file->set_missingsource();
         }
diff --git a/repository/lib.php b/repository/lib.php
index fdf9c3dd9b4..b8c3d20ecc2 100644
--- a/repository/lib.php
+++ b/repository/lib.php
@@ -2752,7 +2752,7 @@ abstract class repository implements cacheable_object {
                     $params['filename']))) {
                 $file->set_missingsource();
             } else {
-                $file->set_synchronized($storedfile->get_contenthash(), $storedfile->get_filesize());
+                $file->set_synchronized($storedfile->get_contenthash(), $storedfile->get_filesize(), 0, $storedfile->get_timemodified());
             }
             return true;
         }