diff --git a/lib/filelib.php b/lib/filelib.php
index 364e43f0289..13d1569e40f 100644
--- a/lib/filelib.php
+++ b/lib/filelib.php
@@ -2017,7 +2017,7 @@ function readfile_accel($file, $mimetype, $accelerate) {
 
     if (is_object($file)) {
         header('Etag: "' . $file->get_contenthash() . '"');
-        if (isset($_SERVER['HTTP_IF_NONE_MATCH']) and $_SERVER['HTTP_IF_NONE_MATCH'] === $file->get_contenthash()) {
+        if (isset($_SERVER['HTTP_IF_NONE_MATCH']) and trim($_SERVER['HTTP_IF_NONE_MATCH'], '"') === $file->get_contenthash()) {
             header('HTTP/1.1 304 Not Modified');
             return;
         }