diff --git a/lib/ace/background_tokenizer.js b/lib/ace/background_tokenizer.js
index 6e2ef93f..6ef3cebe 100644
--- a/lib/ace/background_tokenizer.js
+++ b/lib/ace/background_tokenizer.js
@@ -240,12 +240,9 @@ var BackgroundTokenizer = function(tokenizer, editor) {
         var data = this.tokenizer.getLineTokens(line, state);
         if (overflow) {
             data.tokens.push(overflow);
-            data.state = null;
+            data.state = "start";
         }
 
-        if (data.state == "start" && this.states[row] == null)
-            this.states[row] = "start";
-
         if (this.states[row] !== data.state) {
             this.states[row] = data.state;
             this.lines[row + 1] = null;
diff --git a/lib/ace/background_tokenizer_test.js b/lib/ace/background_tokenizer_test.js
new file mode 100644
index 00000000..192d1f2b
--- /dev/null
+++ b/lib/ace/background_tokenizer_test.js
@@ -0,0 +1,92 @@
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is Ajax.org Code Editor (ACE).
+ *
+ * The Initial Developer of the Original Code is
+ * Ajax.org B.V.
+ * Portions created by the Initial Developer are Copyright (C) 2010
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *      Harutyun Amirjanyan <harutyun@c9.io>
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+if (typeof process !== "undefined") {
+    require("amd-loader");
+}
+
+define(function(require, exports, module) {
+"use strict";
+
+var EditSession = require("./edit_session").EditSession;
+var JavaScriptMode = require("./mode/javascript").Mode;
+var Range = require("./range").Range;
+var assert = require("./test/assertions");
+
+function forceTokenize(session){
+    for (var i = 0, l = session.getLength(); i < l; i++)
+        session.getTokens(i)
+}
+
+function testStates(session, states) {
+	for (var i = 0, l = session.getLength(); i < l; i++)
+		assert.equal(session.bgTokenizer.states[i], states[i])
+	assert.ok(l == states.length)
+}
+
+module.exports = {
+
+    "test background tokenizer update on session change" : function() {
+        var doc = new EditSession([
+			"/*",
+			"*/",
+			"var juhu"
+		]);
+		doc.setMode("ace/mode/javascript")  
+		
+		forceTokenize(doc)
+        testStates(doc, ["comment", "start", "start"])
+		
+		doc.remove(new Range(0,2,1,2))
+		testStates(doc, [null, "start"])
+		
+		forceTokenize(doc)
+        testStates(doc, ["comment", "comment"])
+		
+		doc.insert({row:0, column:2}, "\n*/")
+		testStates(doc, [undefined, undefined, "comment"])
+		
+		forceTokenize(doc)
+        testStates(doc, ["comment", "start", "start"])
+    }
+};
+
+});
+
+if (typeof module !== "undefined" && module === require.main) {
+    require("asyncjs").test.testcase(module.exports).exec()
+}
diff --git a/lib/ace/test/all_browser.js b/lib/ace/test/all_browser.js
index b9987b69..934149e4 100644
--- a/lib/ace/test/all_browser.js
+++ b/lib/ace/test/all_browser.js
@@ -11,6 +11,7 @@ var log = document.getElementById("log")
 
 var testNames = [
     "ace/anchor_test",
+    "ace/background_tokenizer_test",
     "ace/commands/command_manager_test",
     "ace/document_test",
     "ace/edit_session_test",