diff --git a/lib/ace/edit_session.js b/lib/ace/edit_session.js
index 9689ea5c..1de03147 100644
--- a/lib/ace/edit_session.js
+++ b/lib/ace/edit_session.js
@@ -268,7 +268,7 @@ var EditSession = function(text, mode) {
             this.$informUndoManager.schedule();
         }
 
-        this.bgTokenizer.$updateOnChange(delta);
+        this.bgTokenizer && this.bgTokenizer.$updateOnChange(delta);
         this._signal("change", e);
     };
 
@@ -276,8 +276,6 @@ var EditSession = function(text, mode) {
     * Sets the session text.
     * @param {String} text The new text to place
     *
-    *
-    *
     **/
     this.setValue = function(text) {
         this.doc.setValue(text);
@@ -957,12 +955,11 @@ var EditSession = function(text, mode) {
         }
     };
 
-
     this.$stopWorker = function() {
-        if (this.$worker)
+        if (this.$worker) {
             this.$worker.terminate();
-
-        this.$worker = null;
+            this.$worker = null;
+        }
     };
 
     this.$startWorker = function() {
@@ -2400,7 +2397,15 @@ var EditSession = function(text, mode) {
      */
     this.$setFontMetrics = function(fm) {
         // todo
-    }
+    };
+    
+    this.destroy = function() {
+        if (this.bgTokenizer) {
+            this.bgTokenizer.setDocument(null);
+            this.bgTokenizer = null;
+        }
+        this.$stopWorker();
+    };
 
     // For every keystroke this gets called once per char in the whole doc!!
     // Wouldn't hurt to make it a bit faster for c >= 0x1100
diff --git a/lib/ace/editor.js b/lib/ace/editor.js
index 83782f06..a62f1527 100644
--- a/lib/ace/editor.js
+++ b/lib/ace/editor.js
@@ -94,7 +94,8 @@ var Editor = function(renderer, session) {
     
     this._$emitInputEvent = lang.delayedCall(function() {
         this._signal("input", {});
-        this.session.bgTokenizer && this.session.bgTokenizer.scheduleStart();
+        if (this.session && this.session.bgTokenizer)
+            this.session.bgTokenizer.scheduleStart();
     }.bind(this));
     
     this.on("change", function(_, _self) {
@@ -384,6 +385,9 @@ var Editor = function(renderer, session) {
             this.onChangeAnnotation();
             this.session.getUseWrapMode() && this.renderer.adjustWrapLimit();
             this.renderer.updateFull();
+        } else {
+            this.selection = null;
+            this.renderer.setSession(session);
         }
 
         this._signal("changeSession", {
@@ -2519,6 +2523,9 @@ var Editor = function(renderer, session) {
     this.destroy = function() {
         this.renderer.destroy();
         this._signal("destroy", this);
+        if (this.session) {
+            this.session.destroy();
+        }
     };
 
     /**
diff --git a/lib/ace/layer/gutter.js b/lib/ace/layer/gutter.js
index 7b206f61..13ee8a25 100644
--- a/lib/ace/layer/gutter.js
+++ b/lib/ace/layer/gutter.js
@@ -58,7 +58,8 @@ var Gutter = function(parentEl) {
         if (this.session)
             this.session.removeEventListener("change", this.$updateAnnotations);
         this.session = session;
-        session.on("change", this.$updateAnnotations);
+        if (session)
+            session.on("change", this.$updateAnnotations);
     };
 
     this.addGutterDecoration = function(row, className){
diff --git a/lib/ace/layer/text.js b/lib/ace/layer/text.js
index 748d2231..7c3aa053 100644
--- a/lib/ace/layer/text.js
+++ b/lib/ace/layer/text.js
@@ -95,7 +95,8 @@ var Text = function(parentEl) {
     };
     this.setSession = function(session) {
         this.session = session;
-        this.$computeTabString();
+        if (session)
+            this.$computeTabString();
     };
 
     this.showInvisibles = false;
diff --git a/lib/ace/multi_select.js b/lib/ace/multi_select.js
index ef0f7a2e..afe36620 100644
--- a/lib/ace/multi_select.js
+++ b/lib/ace/multi_select.js
@@ -890,12 +890,12 @@ function isSamePoint(p1, p2) {
 // adds multicursor support to a session
 exports.onSessionChange = function(e) {
     var session = e.session;
-    if (!session.multiSelect) {
+    if (session && !session.multiSelect) {
         session.$selectionMarkers = [];
         session.selection.$initRangeList();
         session.multiSelect = session.selection;
     }
-    this.multiSelect = session.multiSelect;
+    this.multiSelect = session && session.multiSelect;
 
     var oldSession = e.oldSession;
     if (oldSession) {
@@ -907,16 +907,16 @@ exports.onSessionChange = function(e) {
         oldSession.multiSelect.anchor.off("change",  this.$checkMultiselectChange);
     }
 
-    session.multiSelect.on("addRange", this.$onAddRange);
-    session.multiSelect.on("removeRange", this.$onRemoveRange);
-    session.multiSelect.on("multiSelect", this.$onMultiSelect);
-    session.multiSelect.on("singleSelect", this.$onSingleSelect);
-    session.multiSelect.lead.on("change",  this.$checkMultiselectChange);
-    session.multiSelect.anchor.on("change",  this.$checkMultiselectChange);
-    
-    // this.$onSelectionChange = this.onSelectionChange.bind(this);
+    if (session) {
+        session.multiSelect.on("addRange", this.$onAddRange);
+        session.multiSelect.on("removeRange", this.$onRemoveRange);
+        session.multiSelect.on("multiSelect", this.$onMultiSelect);
+        session.multiSelect.on("singleSelect", this.$onSingleSelect);
+        session.multiSelect.lead.on("change",  this.$checkMultiselectChange);
+        session.multiSelect.anchor.on("change",  this.$checkMultiselectChange);
+    }
 
-    if (this.inMultiSelectMode != session.selection.inMultiSelectMode) {
+    if (session && this.inMultiSelectMode != session.selection.inMultiSelectMode) {
         if (session.selection.inMultiSelectMode)
             this.$onMultiSelect();
         else
diff --git a/lib/ace/virtual_renderer.js b/lib/ace/virtual_renderer.js
index d3e26758..4cb7af38 100644
--- a/lib/ace/virtual_renderer.js
+++ b/lib/ace/virtual_renderer.js
@@ -232,10 +232,7 @@ var VirtualRenderer = function(container, theme) {
             this.session.doc.off("changeNewLineMode", this.onChangeNewLineMode);
             
         this.session = session;
-        if (!session)
-            return;
-        
-        if (this.scrollMargin.top && session.getScrollTop() <= 0)
+        if (session && this.scrollMargin.top && session.getScrollTop() <= 0)
             session.setScrollTop(-this.scrollMargin.top);
 
         this.$cursorLayer.setSession(session);
@@ -243,6 +240,9 @@ var VirtualRenderer = function(container, theme) {
         this.$markerFront.setSession(session);
         this.$gutterLayer.setSession(session);
         this.$textLayer.setSession(session);
+        if (!session)
+            return;
+        
         this.$loop.schedule(this.CHANGE_FULL);
         this.session.$setFontMetrics(this.$fontMetrics);