diff --git a/lib/ace/background_tokenizer.js b/lib/ace/background_tokenizer.js
index c500120acce..a6b87ccc19c 100644
--- a/lib/ace/background_tokenizer.js
+++ b/lib/ace/background_tokenizer.js
@@ -245,6 +245,14 @@ var BackgroundTokenizer = function(tokenizer, editor) {
         return this.lines[row] = data.tokens;
     };
 
+    this.cleanup = function() {
+        this.running = false;
+        this.lines = [];
+        this.states = [];
+        this.currentLine = 0;
+        this.removeAllListeners();
+    };
+
 }).call(BackgroundTokenizer.prototype);
 
 exports.BackgroundTokenizer = BackgroundTokenizer;
diff --git a/lib/ace/edit_session.js b/lib/ace/edit_session.js
index 72f10444af2..eabc89ac667 100644
--- a/lib/ace/edit_session.js
+++ b/lib/ace/edit_session.js
@@ -153,6 +153,15 @@ var EditSession = function(text, mode) {
     this.$foldData.toString = function() {
         return this.join("\n");
     };
+
+    // Set default background tokenizer with Text mode until editor session mode is set 
+    this.bgTokenizer = new BackgroundTokenizer((new TextMode()).getTokenizer(), this);
+
+    var _self = this;
+    this.bgTokenizer.on("update", function(e) {
+        _self._signal("tokenizerUpdate", e);
+    });
+
     this.on("changeFold", this.onChangeFold.bind(this));
     this.$onChange = this.onChange.bind(this);
 
@@ -166,6 +175,8 @@ var EditSession = function(text, mode) {
     config.resetOptions(this);
     this.setMode(mode);
     config._signal("session", this);
+
+    this.destroyed = false;
 };
 
 
@@ -188,8 +199,7 @@ EditSession.$uid = 0;
         this.doc = doc;
         doc.on("change", this.$onChange);
 
-        if (this.bgTokenizer)
-            this.bgTokenizer.setDocument(this.getDocument());
+        this.bgTokenizer.setDocument(this.getDocument());
 
         this.resetCaches();
     };
@@ -244,7 +254,7 @@ EditSession.$uid = 0;
         this.$wrapData = [];
         this.$rowLengthCache = [];
         this.$resetRowCache(0);
-        if (this.bgTokenizer)
+        if (!this.destroyed)
             this.bgTokenizer.start(0);
     };
 
@@ -273,7 +283,7 @@ EditSession.$uid = 0;
             this.$informUndoManager.schedule();
         }
 
-        this.bgTokenizer && this.bgTokenizer.$updateOnChange(delta);
+        this.bgTokenizer.$updateOnChange(delta);
         this._signal("change", delta);
     };
 
@@ -914,16 +924,7 @@ EditSession.$uid = 0;
             tokenizer.on("update", onReloadTokenizer);
         }
 
-        if (!this.bgTokenizer) {
-            this.bgTokenizer = new BackgroundTokenizer(tokenizer);
-            var _self = this;
-            this.bgTokenizer.on("update", function(e) {
-                _self._signal("tokenizerUpdate", e);
-            });
-        } else {
-            this.bgTokenizer.setTokenizer(tokenizer);
-        }
-
+        this.bgTokenizer.setTokenizer(tokenizer);
         this.bgTokenizer.setDocument(this.getDocument());
 
         this.tokenRe = mode.tokenRe;
@@ -2398,9 +2399,10 @@ EditSession.$uid = 0;
     };
     
     this.destroy = function() {
-        if (this.bgTokenizer) {
+        if (!this.destroyed) {
             this.bgTokenizer.setDocument(null);
-            this.bgTokenizer = null;
+            this.bgTokenizer.cleanup();
+            this.destroyed = true;
         }
         this.$stopWorker();
         this.removeAllListeners();
diff --git a/lib/ace/edit_session_test.js b/lib/ace/edit_session_test.js
index e185f585eb7..0045504dd15 100644
--- a/lib/ace/edit_session_test.js
+++ b/lib/ace/edit_session_test.js
@@ -1143,6 +1143,16 @@ module.exports = {
                 next();
             });
         }, 0);
+    },
+
+    "test: sets destroyed flag when destroy called and tokenizer is never null": function() {
+        var session = new EditSession(["foo bar foo bar"]);
+        assert.notEqual(session.bgTokenizer, null);
+        assert.equal(session.destroyed, false);
+
+        session.destroy();
+        assert.equal(session.destroyed, true);
+        assert.notEqual(session.bgTokenizer, null);
     }
 };
 });
diff --git a/lib/ace/editor.js b/lib/ace/editor.js
index 740b0477784..cac7397b87b 100644
--- a/lib/ace/editor.js
+++ b/lib/ace/editor.js
@@ -99,7 +99,7 @@ var Editor = function(renderer, session, options) {
     
     this._$emitInputEvent = lang.delayedCall(function() {
         this._signal("input", {});
-        if (this.session && this.session.bgTokenizer)
+        if (this.session && !this.session.destroyed)
             this.session.bgTokenizer.scheduleStart();
     }.bind(this));
     
@@ -402,7 +402,7 @@ Editor.$uid = 0;
         oldSession && oldSession._signal("changeEditor", {oldEditor: this});
         session && session._signal("changeEditor", {editor: this});
         
-        if (session && session.bgTokenizer)
+        if (session && !session.destroyed)
             session.bgTokenizer.scheduleStart();
     };
 
@@ -532,7 +532,7 @@ Editor.$uid = 0;
         setTimeout(function () {
             self.$highlightPending = false;
             var session = self.session;
-            if (!session || !session.bgTokenizer) return;
+            if (!session || session.destroyed) return;
             if (session.$bracketHighlight) {
                 session.$bracketHighlight.markerIds.forEach(function(id) {
                     session.removeMarker(id);
@@ -581,7 +581,7 @@ Editor.$uid = 0;
             self.$highlightTagPending = false;
             
             var session = self.session;
-            if (!session || !session.bgTokenizer) return;
+            if (!session || session.destroyed) return;
             
             var pos = self.getCursorPosition();
             var iterator = new TokenIterator(self.session, pos.row, pos.column);