diff --git a/lib/ace/editor.js b/lib/ace/editor.js
index 0efbdd93..300e4399 100644
--- a/lib/ace/editor.js
+++ b/lib/ace/editor.js
@@ -289,14 +289,13 @@ var Editor = function(renderer, session) {
      * Sets a new editsession to use. This method also emits the `'changeSession'` event.
      * @param {EditSession} session The new session to use
      *
-     *
      **/
     this.setSession = function(session) {
         if (this.session == session)
             return;
 
-        if (this.session) {
-            var oldSession = this.session;
+        var oldSession = this.session;
+        if (oldSession) {
             this.session.removeEventListener("change", this.$onDocumentChange);
             this.session.removeEventListener("changeMode", this.$onChangeMode);
             this.session.removeEventListener("tokenizerUpdate", this.$onTokenizerUpdate);
@@ -318,76 +317,80 @@ var Editor = function(renderer, session) {
         }
 
         this.session = session;
-
-        this.$onDocumentChange = this.onDocumentChange.bind(this);
-        session.addEventListener("change", this.$onDocumentChange);
-        this.renderer.setSession(session);
-
-        this.$onChangeMode = this.onChangeMode.bind(this);
-        session.addEventListener("changeMode", this.$onChangeMode);
-
-        this.$onTokenizerUpdate = this.onTokenizerUpdate.bind(this);
-        session.addEventListener("tokenizerUpdate", this.$onTokenizerUpdate);
-
-        this.$onChangeTabSize = this.renderer.onChangeTabSize.bind(this.renderer);
-        session.addEventListener("changeTabSize", this.$onChangeTabSize);
-
-        this.$onChangeWrapLimit = this.onChangeWrapLimit.bind(this);
-        session.addEventListener("changeWrapLimit", this.$onChangeWrapLimit);
-
-        this.$onChangeWrapMode = this.onChangeWrapMode.bind(this);
-        session.addEventListener("changeWrapMode", this.$onChangeWrapMode);
-
-        this.$onChangeFold = this.onChangeFold.bind(this);
-        session.addEventListener("changeFold", this.$onChangeFold);
-
-        this.$onChangeFrontMarker = this.onChangeFrontMarker.bind(this);
-        this.session.addEventListener("changeFrontMarker", this.$onChangeFrontMarker);
-
-        this.$onChangeBackMarker = this.onChangeBackMarker.bind(this);
-        this.session.addEventListener("changeBackMarker", this.$onChangeBackMarker);
-
-        this.$onChangeBreakpoint = this.onChangeBreakpoint.bind(this);
-        this.session.addEventListener("changeBreakpoint", this.$onChangeBreakpoint);
-
-        this.$onChangeAnnotation = this.onChangeAnnotation.bind(this);
-        this.session.addEventListener("changeAnnotation", this.$onChangeAnnotation);
-
-        this.$onCursorChange = this.onCursorChange.bind(this);
-        this.session.addEventListener("changeOverwrite", this.$onCursorChange);
-
-        this.$onScrollTopChange = this.onScrollTopChange.bind(this);
-        this.session.addEventListener("changeScrollTop", this.$onScrollTopChange);
-
-        this.$onScrollLeftChange = this.onScrollLeftChange.bind(this);
-        this.session.addEventListener("changeScrollLeft", this.$onScrollLeftChange);
-
-        this.selection = session.getSelection();
-        this.selection.addEventListener("changeCursor", this.$onCursorChange);
-
-        this.$onSelectionChange = this.onSelectionChange.bind(this);
-        this.selection.addEventListener("changeSelection", this.$onSelectionChange);
-
-        this.onChangeMode();
-
-        this.$blockScrolling += 1;
-        this.onCursorChange();
-        this.$blockScrolling -= 1;
-
-        this.onScrollTopChange();
-        this.onScrollLeftChange();
-        this.onSelectionChange();
-        this.onChangeFrontMarker();
-        this.onChangeBackMarker();
-        this.onChangeBreakpoint();
-        this.onChangeAnnotation();
-        this.session.getUseWrapMode() && this.renderer.adjustWrapLimit();
-        this.renderer.updateFull();
+        if (session) {
+            this.$onDocumentChange = this.onDocumentChange.bind(this);
+            session.addEventListener("change", this.$onDocumentChange);
+            this.renderer.setSession(session);
+    
+            this.$onChangeMode = this.onChangeMode.bind(this);
+            session.addEventListener("changeMode", this.$onChangeMode);
+    
+            this.$onTokenizerUpdate = this.onTokenizerUpdate.bind(this);
+            session.addEventListener("tokenizerUpdate", this.$onTokenizerUpdate);
+    
+            this.$onChangeTabSize = this.renderer.onChangeTabSize.bind(this.renderer);
+            session.addEventListener("changeTabSize", this.$onChangeTabSize);
+    
+            this.$onChangeWrapLimit = this.onChangeWrapLimit.bind(this);
+            session.addEventListener("changeWrapLimit", this.$onChangeWrapLimit);
+    
+            this.$onChangeWrapMode = this.onChangeWrapMode.bind(this);
+            session.addEventListener("changeWrapMode", this.$onChangeWrapMode);
+    
+            this.$onChangeFold = this.onChangeFold.bind(this);
+            session.addEventListener("changeFold", this.$onChangeFold);
+    
+            this.$onChangeFrontMarker = this.onChangeFrontMarker.bind(this);
+            this.session.addEventListener("changeFrontMarker", this.$onChangeFrontMarker);
+    
+            this.$onChangeBackMarker = this.onChangeBackMarker.bind(this);
+            this.session.addEventListener("changeBackMarker", this.$onChangeBackMarker);
+    
+            this.$onChangeBreakpoint = this.onChangeBreakpoint.bind(this);
+            this.session.addEventListener("changeBreakpoint", this.$onChangeBreakpoint);
+    
+            this.$onChangeAnnotation = this.onChangeAnnotation.bind(this);
+            this.session.addEventListener("changeAnnotation", this.$onChangeAnnotation);
+    
+            this.$onCursorChange = this.onCursorChange.bind(this);
+            this.session.addEventListener("changeOverwrite", this.$onCursorChange);
+    
+            this.$onScrollTopChange = this.onScrollTopChange.bind(this);
+            this.session.addEventListener("changeScrollTop", this.$onScrollTopChange);
+    
+            this.$onScrollLeftChange = this.onScrollLeftChange.bind(this);
+            this.session.addEventListener("changeScrollLeft", this.$onScrollLeftChange);
+    
+            this.selection = session.getSelection();
+            this.selection.addEventListener("changeCursor", this.$onCursorChange);
+    
+            this.$onSelectionChange = this.onSelectionChange.bind(this);
+            this.selection.addEventListener("changeSelection", this.$onSelectionChange);
+    
+            this.onChangeMode();
+    
+            this.$blockScrolling += 1;
+            this.onCursorChange();
+            this.$blockScrolling -= 1;
+    
+            this.onScrollTopChange();
+            this.onScrollLeftChange();
+            this.onSelectionChange();
+            this.onChangeFrontMarker();
+            this.onChangeBackMarker();
+            this.onChangeBreakpoint();
+            this.onChangeAnnotation();
+            this.session.getUseWrapMode() && this.renderer.adjustWrapLimit();
+            this.renderer.updateFull();
+        }
 
         this._signal("changeSession", {
             session: session,
             oldSession: oldSession
         });
+        
+        oldSession && oldSession._signal("changeEditor", {oldEditor: this});
+        session && session._signal("changeEditor", {editor: this});
     };
 
     /**