diff --git a/lib/ace/edit_session.js b/lib/ace/edit_session.js
index ce959e57..e9e2a66a 100644
--- a/lib/ace/edit_session.js
+++ b/lib/ace/edit_session.js
@@ -93,6 +93,7 @@ var EditSession = function(text, mode) {
 
     this.setValue = function(text) {
       this.doc.setValue(text);
+      this.$deltas = [];
     };
 
     this.getValue =
@@ -479,36 +480,41 @@ var EditSession = function(text, mode) {
     };
     
     this.undoChanges = function(deltas) {
-        this.selection.clearSelection();
+        if (!deltas.length)
+            return;
+            
         this.$fromUndo = true;
-        for (var i=deltas.length-1; i>=0; i--) {
-            var delta = deltas[i];
-            if (delta.action == "insertText") {
-                this.remove(delta.range, true);
-                this.selection.moveCursorToPosition(delta.range.start);
-            } else {
-                this.insert(delta.range.start, delta.text, true);
-                this.selection.clearSelection();
-            }
-        }
+        this.doc.revertDeltas(deltas);
         this.$fromUndo = false;
+        
+        // update the selection
+        var firstDelta = deltas[0];
+        var lastDelta = deltas[deltas.length-1];
+        
+        this.selection.clearSelection();
+        if (firstDelta.action == "insertText" || firstDelta.action == "insertLines")
+            this.selection.moveCursorToPosition(firstDelta.range.start);
+        if (firstDelta.action == "removeText" || firstDelta.action == "removeLines")
+            this.selection.setSelectionRange(Range.fromPoints(firstDelta.range.start, lastDelta.range.end));
     },
 
     this.redoChanges = function(deltas) {
-        this.selection.clearSelection();
-        
+        if (!deltas.length)
+            return;
+            
         this.$fromUndo = true;
-        for (var i=0; i<deltas.length; i++) {
-            var delta = deltas[i];
-            if (delta.action == "insertText") {
-                this.insert(delta.range.start, delta.text, true);
-                this.selection.setSelectionRange(delta.range);
-            } else {
-                this.remove(delta.range, true);
-                this.selection.moveCursorToPosition(delta.range.start);
-            }
-        }
+        this.doc.applyDeltas(deltas);
         this.$fromUndo = false;
+        
+        // update the selection
+        var firstDelta = deltas[0];
+        var lastDelta = deltas[deltas.length-1];
+        
+        this.selection.clearSelection();
+        if (firstDelta.action == "insertText" || firstDelta.action == "insertLines")
+            this.selection.setSelectionRange(Range.fromPoints(firstDelta.range.start, lastDelta.range.end));
+        if (firstDelta.action == "removeText" || firstDelta.action == "removeLines")
+            this.selection.moveCursorToPosition(firstDelta.range.start);
     },
 
     this.replace = function(range, text) {