diff --git a/filter/tex/pix.php b/filter/tex/pix.php
index 679d436bd39..e4697cf48ff 100644
--- a/filter/tex/pix.php
+++ b/filter/tex/pix.php
@@ -64,7 +64,10 @@ define('NO_MOODLE_COOKIES', true); // Because it interferes with caching
     }
 
     if (file_exists($pathname)) {
-        send_file($pathname, $image);
+        send_file($pathname, $image, YEARSECS, 0, false, false, '', false, [
+            'cacheability' => 'public',
+            'immutable' => true,
+        ]);
     } else {
         if (debugging()) {
             echo "The shell command<br />$cmd<br />returned status = $status<br />\n";