diff --git a/lib/outputrequirementslib.php b/lib/outputrequirementslib.php
index 5d9038428e8..93c5cbea43b 100644
--- a/lib/outputrequirementslib.php
+++ b/lib/outputrequirementslib.php
@@ -973,9 +973,9 @@ class page_requirements_manager {
         }
 
         if (debugging('', DEBUG_DEVELOPER)) {
-            $code .= '<script src="'.$this->yui3loader->base.'yui/yui-debug.js"></script>';
+            $code .= '<script type="text/javascript" src="'.$this->yui3loader->base.'yui/yui-debug.js"></script>';
         } else {
-            $code .= '<script src="'.$this->yui3loader->base.'yui/yui-min.js"></script>';
+            $code .= '<script type="text/javascript" src="'.$this->yui3loader->base.'yui/yui-min.js"></script>';
         }
 
         return $code;