diff --git a/lib/ace/placeholder.js b/lib/ace/placeholder.js
index f0fa5b46..f8141690 100644
--- a/lib/ace/placeholder.js
+++ b/lib/ace/placeholder.js
@@ -60,7 +60,7 @@ var PlaceHolder = function(session, length, pos, others, mainClass, othersClass)
     
     this.$pos = pos;
     // Used for reset
-    this.$undoStackDepth = session.getUndoManager().$undoStack ? session.getUndoManager().$undoStack.length : -1;
+    this.$undoStackDepth = session.getUndoManager().$undostack ? session.getUndoManager().$undostack.length : -1;
     this.setup();
 
     session.selection.on("changeCursor", this.$onCursorChange);
@@ -202,7 +202,7 @@ var PlaceHolder = function(session, length, pos, others, mainClass, othersClass)
         if(this.$undoStackDepth === -1)
             throw Error("Canceling placeholders only supported with undo manager attached to session.");
         var undoManager = this.session.getUndoManager();
-        var undosRequired = undoManager.$undoStack.length - this.$undoStackDepth;
+        var undosRequired = undoManager.$undostack.length - this.$undoStackDepth;
         for (var i = 0; i < undosRequired; i++) {
             undoManager.undo(true);
         }