diff --git a/notebook/static/notebook/js/notebook.js b/notebook/static/notebook/js/notebook.js
index 52624834d..df9a23825 100644
--- a/notebook/static/notebook/js/notebook.js
+++ b/notebook/static/notebook/js/notebook.js
@@ -113,6 +113,7 @@ define(function (require) {
                         }
                     }, function (err) {
                         console.log("No CodeMirror mode: " + lang);
+                        console.log("Require CodeMirror mode error: " + err);
                         callback(null, code);
                     });
                 }