diff --git a/lib/editor/tinymce/module.js b/lib/editor/tinymce/module.js
index d3118ef0f33..4b227d132bb 100644
--- a/lib/editor/tinymce/module.js
+++ b/lib/editor/tinymce/module.js
@@ -45,6 +45,7 @@ M.editor_tinymce.init_editor = function(Y, editorid, options) {
         M.editor_tinymce.initialised = true;
         M.util.js_pending('editors');
         options.oninit = "M.editor_tinymce.init_callback";
+        options.onchange_callback = "M.editor_tinymce.onchange_callback";
     }
 
     M.editor_tinymce.editor_options[editorid] = options;
@@ -92,6 +93,12 @@ M.editor_tinymce.init_callback = function() {
     M.util.js_complete('editors');
 }
 
+M.editor_tinymce.onchange_callback = function(editorinstance) {
+    // We need to keep the underlying textarea in sync so that when the form
+    // validator is triggered, it has the value property up-to-date.
+    editorinstance.save();
+};
+
 M.editor_tinymce.init_filepicker = function(Y, editorid, options) {
     M.editor_tinymce.filepicker_options[editorid] = options;
 };