diff --git a/HISTORY.md b/HISTORY.md
index ab4da30..6fd8904 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -3,6 +3,12 @@
 https://github.com/josdejong/jsoneditor
 
 
+## not yet released, version 5.5.12
+
+- Fixed #309: already loaded version of Ace being overwritten by the embedded
+  version of JSONEditor.
+
+
 ## 2017-01-06, version 5.5.11
 
 - Fixed embedded version of jsoneditor ace theme not being loaded in
diff --git a/src/js/ace/index.js b/src/js/ace/index.js
index cc41440..ec6541e 100644
--- a/src/js/ace/index.js
+++ b/src/js/ace/index.js
@@ -1,8 +1,21 @@
-// load brace
-var ace = require('brace');
+var ace
+if (window.ace) {
+  // use the already loaded instance of Ace
+  ace = window.ace
+}
+else {
+  try {
+    // load brace
+    ace = require('brace');
 
-// load required ace modules
-require('brace/mode/json');
-require('brace/ext/searchbox');
+    // load required Ace plugins
+    require('brace/mode/json');
+    require('brace/ext/searchbox');
+  }
+  catch (err) {
+    // failed to load brace (can be minimalist bundle).
+    // No worries, the editor will fall back to plain text if needed.
+  }
+}
 
 module.exports = ace;
diff --git a/src/js/textmode.js b/src/js/textmode.js
index e27e88a..f8a3e05 100644
--- a/src/js/textmode.js
+++ b/src/js/textmode.js
@@ -1,13 +1,6 @@
 'use strict';
 
-var ace;
-try {
-  ace = require('./ace');
-}
-catch (err) {
-  // failed to load ace, no problem, we will fall back to plain text
-}
-
+var ace = require('./ace');
 var ModeSwitcher = require('./ModeSwitcher');
 var util = require('./util');
 
@@ -53,6 +46,7 @@ textmode.create = function (container, options) {
 
   // grab ace from options if provided
   var _ace = options.ace ? options.ace : ace;
+  // TODO: make the option options.ace deprecated, it's not needed anymore (see #309)
 
   // determine mode
   this.mode = (options.mode == 'code') ? 'code' : 'text';
@@ -66,8 +60,13 @@ textmode.create = function (container, options) {
 
   // determine theme
   this.theme = options.theme || DEFAULT_THEME;
-  if (this.theme === DEFAULT_THEME && window.ace) {
-    require('./ace/theme-jsoneditor');
+  if (this.theme === DEFAULT_THEME && _ace) {
+    try {
+      require('./ace/theme-jsoneditor');
+    }
+    catch (err) {
+      console.error(err);
+    }
   }
 
   var me = this;