diff --git a/HISTORY.md b/HISTORY.md
index 6924458..2b249c8 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -6,6 +6,8 @@ https://github.com/josdejong/jsoneditor
 ## not yet released, version 4.2.2
 
 - Replaced the PNG icon images with SVG. Thanks @1j01.
+- Fixed #149: Memory leak when switching mode from/to `code` mode, web worker
+  of Ace editor wasn't cleaned up.
 - Fixed #234: Remove dependency on a fork of the `jsonlint` project on github.
 - Fixed: disabled `Ctrl+L` quick key to go to a line, instead use the default
   browser behavior of selecting the address bar.
diff --git a/src/js/textmode.js b/src/js/textmode.js
index 7b1f7ee..17a4247 100644
--- a/src/js/textmode.js
+++ b/src/js/textmode.js
@@ -218,6 +218,12 @@ textmode._onKeyDown = function (event) {
  * @private
  */
 textmode._delete = function () {
+  // remove old ace editor
+  if (this.editor) {
+    this.editor.destroy();
+    console.log('destroy');
+  }
+
   if (this.frame && this.container && this.frame.parentNode == this.container) {
     this.container.removeChild(this.frame);
   }