diff --git a/examples/html-editor/index.js b/examples/html-editor/index.js
index 330fadf0..946fdb3a 100644
--- a/examples/html-editor/index.js
+++ b/examples/html-editor/index.js
@@ -18,7 +18,7 @@ window.undoManager = new Y.utils.UndoManager(window.yXmlType, {
 })
 
 document.onkeydown = function interceptUndoRedo (e) {
-  if (e.keyCode === 90 && e.metaKey) {
+  if (e.keyCode === 90 && (e.metaKey || e.ctrlKey)) {
     if (!e.shiftKey) {
       window.undoManager.undo()
     } else {
diff --git a/src/Struct/Item.js b/src/Struct/Item.js
index ae99c984..2f9f87b7 100644
--- a/src/Struct/Item.js
+++ b/src/Struct/Item.js
@@ -51,22 +51,56 @@ export default class Item {
     this._parent = null
     this._parentSub = null
     this._deleted = false
+    this._redone = null
   }
   /**
-   * Copy the effect of struct
+   * Create a operation with the same effect (without position effect)
    */
-  _copy (undeleteChildren, copyPosition) {
-    let struct = new this.constructor()
-    if (copyPosition) {
-      struct._origin = this._left
-      struct._left = this._left
-      struct._right = this
-      struct._right_origin = this
-      struct._parent = this._parent
-      struct._parentSub = this._parentSub
+  _copy () {
+    return new this.constructor()
+  }
+  /**
+   * Redo the effect of this operation.
+   */
+  _redo (y) {
+    if (this._redone !== null) {
+      return this._redone
     }
+    let struct = this._copy()
+    let left = this._left
+    let right = this
+    let parent = this._parent
+    // make sure that parent is redone
+    if (parent._deleted === true && parent._redone === null) {
+      parent._redo(y)
+    }
+    if (parent._redone !== null) {
+      parent = parent._redone
+      // find next cloned items
+      while (left !== null && left._redone === null) {
+        left = left._left
+      }
+      if (left !== null) {
+        left = left._redone
+      }
+      while (right !== null && right._redone === null) {
+        right = right._right
+      }
+      if (right !== null) {
+        right = right._redone
+      }
+    }
+    struct._origin = left
+    struct._left = left
+    struct._right = right
+    struct._right_origin = right
+    struct._parent = parent
+    struct._parentSub = this._parentSub
+    struct._integrate(y)
+    this._redone = struct
     return struct
   }
+
   get _lastId () {
     return new ID(this._id.user, this._id.clock + this._length - 1)
   }
diff --git a/src/Struct/ItemJSON.js b/src/Struct/ItemJSON.js
index f2d773d1..f8d22dd4 100644
--- a/src/Struct/ItemJSON.js
+++ b/src/Struct/ItemJSON.js
@@ -6,8 +6,8 @@ export default class ItemJSON extends Item {
     super()
     this._content = null
   }
-  _copy (undeleteChildren, copyPosition) {
-    let struct = super._copy(undeleteChildren, copyPosition)
+  _copy () {
+    let struct = super._copy()
     struct._content = this._content
     return struct
   }
diff --git a/src/Struct/ItemString.js b/src/Struct/ItemString.js
index 7b888b64..a5a0b90c 100644
--- a/src/Struct/ItemString.js
+++ b/src/Struct/ItemString.js
@@ -6,8 +6,8 @@ export default class ItemString extends Item {
     super()
     this._content = null
   }
-  _copy (undeleteChildren, copyPosition) {
-    let struct = super._copy(undeleteChildren, copyPosition)
+  _copy () {
+    let struct = super._copy()
     struct._content = this._content
     return struct
   }
diff --git a/src/Struct/Type.js b/src/Struct/Type.js
index 734dcdcf..80d93fed 100644
--- a/src/Struct/Type.js
+++ b/src/Struct/Type.js
@@ -79,40 +79,6 @@ export default class Type extends Item {
       type = type._parent
     }
   }
-  _copy (undeleteChildren, copyPosition) {
-    let copy = super._copy(undeleteChildren, copyPosition)
-    let map = new Map()
-    copy._map = map
-    for (let [key, value] of this._map) {
-      if (undeleteChildren.has(value) || !value.deleted) {
-        let _item = value._copy(undeleteChildren, false)
-        _item._parent = copy
-        _item._parentSub = key
-        map.set(key, _item)
-      }
-    }
-    let prevUndeleted = null
-    copy._start = null
-    let item = this._start
-    while (item !== null) {
-      if (undeleteChildren.has(item) || !item.deleted) {
-        let _item = item._copy(undeleteChildren, false)
-        _item._left = prevUndeleted
-        _item._origin = prevUndeleted
-        _item._right = null
-        _item._right_origin = null
-        _item._parent = copy
-        if (prevUndeleted === null) {
-          copy._start = _item
-        } else {
-          prevUndeleted._right = _item
-        }
-        prevUndeleted = _item
-      }
-      item = item._right
-    }
-    return copy
-  }
   _transact (f) {
     const y = this._y
     if (y !== null) {
diff --git a/src/Type/y-xml/YXmlElement.js b/src/Type/y-xml/YXmlElement.js
index 39c4a3ae..e546c8b3 100644
--- a/src/Type/y-xml/YXmlElement.js
+++ b/src/Type/y-xml/YXmlElement.js
@@ -20,8 +20,8 @@ export default class YXmlElement extends YXmlFragment {
       this._domFilter = arg2
     }
   }
-  _copy (undeleteChildren, copyPosition) {
-    let struct = super._copy(undeleteChildren, copyPosition)
+  _copy () {
+    let struct = super._copy()
     struct.nodeName = this.nodeName
     return struct
   }
diff --git a/src/Type/y-xml/YXmlHook.js b/src/Type/y-xml/YXmlHook.js
index 60926148..ee2ce4f7 100644
--- a/src/Type/y-xml/YXmlHook.js
+++ b/src/Type/y-xml/YXmlHook.js
@@ -14,8 +14,8 @@ export default class YXmlHook extends YMap {
       getHook(hookName).fillType(dom, this)
     }
   }
-  _copy (undeleteChildren, copyPosition) {
-    const struct = super._copy(undeleteChildren, copyPosition)
+  _copy () {
+    const struct = super._copy()
     struct.hookName = this.hookName
     return struct
   }
diff --git a/src/Util/UndoManager.js b/src/Util/UndoManager.js
index 9d8a16ef..83b37530 100644
--- a/src/Util/UndoManager.js
+++ b/src/Util/UndoManager.js
@@ -4,11 +4,12 @@ class ReverseOperation {
   constructor (y, transaction) {
     this.created = new Date()
     const beforeState = transaction.beforeState
-    this.toState = new ID(y.userID, y.ss.getState(y.userID) - 1)
     if (beforeState.has(y.userID)) {
+      this.toState = new ID(y.userID, y.ss.getState(y.userID) - 1)
       this.fromState = new ID(y.userID, beforeState.get(y.userID))
     } else {
-      this.fromState = this.toState
+      this.toState = null
+      this.fromState = null
     }
     this.deletedStructs = transaction.deletedStructs
   }
@@ -30,28 +31,28 @@ function applyReverseOperation (y, scope, reverseBuffer) {
     while (!performedUndo && reverseBuffer.length > 0) {
       let undoOp = reverseBuffer.pop()
       // make sure that it is possible to iterate {from}-{to}
-      y.os.getItemCleanStart(undoOp.fromState)
-      y.os.getItemCleanEnd(undoOp.toState)
-      y.os.iterate(undoOp.fromState, undoOp.toState, op => {
-        if (!op._deleted && isStructInScope(y, op, scope)) {
-          performedUndo = true
-          op._delete(y)
-        }
-      })
+      if (undoOp.fromState !== null) {
+        let start = y.os.getItemCleanStart(undoOp.fromState)
+        y.os.getItemCleanEnd(undoOp.toState)
+        console.log(start)
+        y.os.iterate(undoOp.fromState, undoOp.toState, op => {
+          debugger
+          if (op._deleted && op._redone !== null) {
+            op = op._redone
+          }
+          if (op._deleted === false && isStructInScope(y, op, scope)) {
+            performedUndo = true
+            op._delete(y)
+          }
+        })
+      }
       for (let op of undoOp.deletedStructs) {
         if (
           isStructInScope(y, op, scope) &&
-          op._parent !== y &&
-          !op._parent._deleted &&
-          (
-            op._parent._id.user !== y.userID ||
-            op._parent._id.clock < undoOp.fromState.clock ||
-            op._parent._id.clock > undoOp.fromState.clock
-          )
+          op._parent !== y
         ) {
           performedUndo = true
-          op = op._copy(undoOp.deletedStructs, true)
-          op._integrate(y)
+          op._redo(y)
         }
       }
     }