diff --git a/lib/javascript.php b/lib/javascript.php
index f8ad74c8dc9..7e7869fbac1 100644
--- a/lib/javascript.php
+++ b/lib/javascript.php
@@ -30,7 +30,6 @@ define('NO_DEBUG_DISPLAY', true);
 define('ABORT_AFTER_CONFIG', true);
 require('../config.php'); // this stops immediately at the beginning of lib/setup.php
 require_once("$CFG->dirroot/lib/jslib.php");
-require_once("$CFG->dirroot/lib/classes/minify.php");
 
 if ($slashargument = min_get_slash_argument()) {
     $slashargument = ltrim($slashargument, '/');
@@ -93,6 +92,15 @@ if ($rev > 0 and $rev < (time() + 60*60)) {
         js_send_cached($candidate, $etag);
 
     } else {
+        // The JS needs minfifying, so we're gonna have to load our full Moodle
+        // environment to process it..
+        define('ABORT_AFTER_CONFIG_CANCEL', true);
+
+        define('NO_MOODLE_COOKIES', true); // Session not used here.
+        define('NO_UPGRADE_CHECK', true);  // Ignore upgrade check.
+
+        require("$CFG->dirroot/lib/setup.php");
+
         js_write_cache_file_content($candidate, core_minify::js_files($jsfiles));
         // verify nothing failed in cache file creation
         clearstatcache();