diff --git a/lib/ace/editor.js b/lib/ace/editor.js
index 8f051394..f00f74f6 100644
--- a/lib/ace/editor.js
+++ b/lib/ace/editor.js
@@ -278,6 +278,10 @@ var Editor = function(renderer, session) {
     this.setSession = function(session) {
         if (this.session == session)
             return;
+        
+        // make sure operationEnd events are not emitted to wrong session
+        if (this.curOp) this.endOperation();
+        this.curOp = {};
 
         var oldSession = this.session;
         if (oldSession) {
@@ -377,6 +381,8 @@ var Editor = function(renderer, session) {
             oldSession: oldSession
         });
         
+        this.curOp = null;
+        
         oldSession && oldSession._signal("changeEditor", {oldEditor: this});
         session && session._signal("changeEditor", {editor: this});
     };