diff --git a/rollup.browser.js b/rollup.browser.js
index a0b87065..d5f6c137 100644
--- a/rollup.browser.js
+++ b/rollup.browser.js
@@ -19,8 +19,7 @@ export default {
       browser: true
     }),
     commonjs(),
-    // babel(),
-    /*
+    babel(),
     uglify({
       mangle: {
         except: ['YMap', 'Y', 'YArray', 'YText', 'YXmlHook', 'YXmlFragment', 'YXmlElement', 'YXmlEvent', 'YXmlText', 'YEvent', 'YArrayEvent', 'YMapEvent', 'Type', 'Delete', 'ItemJSON', 'ItemString', 'Item']
@@ -36,7 +35,6 @@ export default {
         }
       }
     })
-    */
   ],
   banner: `
 /**
diff --git a/src/MessageHandler/deleteSet.js b/src/MessageHandler/deleteSet.js
index cb4b1c3b..2b54abfc 100644
--- a/src/MessageHandler/deleteSet.js
+++ b/src/MessageHandler/deleteSet.js
@@ -92,7 +92,7 @@ export function readDeleteSet (y, decoder) {
             // delete maximum the len of d
             // else delete as much as possible
             diff = Math.min(n._id.clock - d[0], d[1])
-            // deleteItemRange(y, user, d[0], diff)
+            // deleteItemRange(y, user, d[0], diff, true)
             deletions.push([user, d[0], diff])
           } else {
             // 3)
@@ -100,7 +100,7 @@ export function readDeleteSet (y, decoder) {
             if (d[2] && !n.gc) {
               // d marks as gc'd but n does not
               // then delete either way
-              // deleteItemRange(y, user, d[0], Math.min(diff, d[1]))
+              // deleteItemRange(y, user, d[0], Math.min(diff, d[1]), true)
               deletions.push([user, d[0], Math.min(diff, d[1])])
             }
           }
@@ -117,12 +117,12 @@ export function readDeleteSet (y, decoder) {
       // Adapt the Tree implementation to support delete while iterating
       for (let i = deletions.length - 1; i >= 0; i--) {
         const del = deletions[i]
-        deleteItemRange(y, del[0], del[1], del[2])
+        deleteItemRange(y, del[0], del[1], del[2], true)
       }
       // for the rest.. just apply it
       for (; pos < dv.length; pos++) {
         d = dv[pos]
-        deleteItemRange(y, user, d[0], d[1])
+        deleteItemRange(y, user, d[0], d[1], true)
         // deletions.push([user, d[0], d[1], d[2]])
       }
     }
diff --git a/src/MessageHandler/syncStep1.js b/src/MessageHandler/syncStep1.js
index 8834d9f0..046177c3 100644
--- a/src/MessageHandler/syncStep1.js
+++ b/src/MessageHandler/syncStep1.js
@@ -42,7 +42,15 @@ export function writeStructs (y, encoder, ss) {
   for (let user of y.ss.state.keys()) {
     let clock = ss.get(user) || 0
     if (user !== RootFakeUserID) {
-      y.os.iterate(new ID(user, clock), new ID(user, Number.MAX_VALUE), function (struct) {
+      const minBound = new ID(user, clock)
+      const overlappingLeft = y.os.findPrev(minBound)
+      const rightID = overlappingLeft === null ? null : overlappingLeft._id
+      if (rightID !== null && rightID.user === user && rightID.clock + overlappingLeft._length > clock) {
+        const struct = overlappingLeft._clonePartial(clock - rightID.clock)
+        struct._toBinary(encoder)
+        len++
+      }
+      y.os.iterate(minBound, new ID(user, Number.MAX_VALUE), function (struct) {
         struct._toBinary(encoder)
         len++
       })
diff --git a/src/Store/DeleteStore.js b/src/Store/DeleteStore.js
index eb5b1a9e..f35bd928 100644
--- a/src/Store/DeleteStore.js
+++ b/src/Store/DeleteStore.js
@@ -1,3 +1,4 @@
+
 import Tree from '../Util/Tree.js'
 import ID from '../Util/ID/ID.js'
 
diff --git a/src/Struct/Delete.js b/src/Struct/Delete.js
index 8e1e7c21..74bdbeb1 100644
--- a/src/Struct/Delete.js
+++ b/src/Struct/Delete.js
@@ -7,7 +7,7 @@ import { logID } from '../MessageHandler/messageToString.js'
  * Delete all items in an ID-range
  * TODO: implement getItemCleanStartNode for better performance (only one lookup)
  */
-export function deleteItemRange (y, user, clock, range) {
+export function deleteItemRange (y, user, clock, range, gcChildren) {
   const createDelete = y.connector !== null && y.connector._forwardAppliedStructs
   let item = y.os.getItemCleanStart(new ID(user, clock))
   if (item !== null) {
@@ -24,7 +24,7 @@ export function deleteItemRange (y, user, clock, range) {
         const nodeVal = node.val
         if (!nodeVal._deleted) {
           nodeVal._splitAt(y, range)
-          nodeVal._delete(y, createDelete, true)
+          nodeVal._delete(y, createDelete, gcChildren)
         }
         const nodeLen = nodeVal._length
         range -= nodeLen
@@ -100,7 +100,7 @@ export default class Delete {
     if (!locallyCreated) {
       // from remote
       const id = this._targetID
-      deleteItemRange(y, id.user, id.clock, this._length)
+      deleteItemRange(y, id.user, id.clock, this._length, false)
     } else if (y.connector !== null) {
       // from local
       y.connector.broadcastStruct(this)
diff --git a/src/Struct/GC.js b/src/Struct/GC.js
index 1a90c888..a23d55b6 100644
--- a/src/Struct/GC.js
+++ b/src/Struct/GC.js
@@ -36,7 +36,6 @@ export default class GC {
       n._length += next._length
       y.os.delete(next._id)
     }
-
     if (id.user !== RootFakeUserID) {
       if (y.connector !== null && (y.connector._forwardAppliedStructs || id.user === y.userID)) {
         y.connector.broadcastStruct(this)
@@ -85,4 +84,11 @@ export default class GC {
   _splitAt () {
     return this
   }
+
+  _clonePartial (diff) {
+    const gc = new GC()
+    gc._id = new ID(this._id.user, this._id.clock + diff)
+    gc._length = this._length - diff
+    return gc
+  }
 }
\ No newline at end of file
diff --git a/src/Struct/Item.js b/src/Struct/Item.js
index 9b76e14b..1ff928f2 100644
--- a/src/Struct/Item.js
+++ b/src/Struct/Item.js
@@ -1,6 +1,6 @@
 import { getStructReference } from '../Util/structReferences.js'
 import ID from '../Util/ID/ID.js'
-import { RootFakeUserID } from '../Util/ID/RootID.js'
+import { default as RootID, RootFakeUserID } from '../Util/ID/RootID.js'
 import Delete from './Delete.js'
 import { transactionTypeChanged } from '../Transaction.js'
 import GC from './GC.js'
@@ -486,7 +486,12 @@ export default class Item {
       const parentID = decoder.readID()
       // parent does not change, so we don't have to search for it again
       if (this._parent === null) {
-        const parent = y.os.get(parentID)
+        let parent
+        if (parentID.constructor === RootID) {
+          parent = y.os.get(parentID)
+        } else {
+          parent = y.os.getItem(parentID)
+        }
         if (parent === null) {
           missing.push(parentID)
         } else {
diff --git a/src/Struct/Type.js b/src/Struct/Type.js
index 2d96dcc2..44f075ad 100644
--- a/src/Struct/Type.js
+++ b/src/Struct/Type.js
@@ -214,7 +214,10 @@ export default class Type extends Item {
    * @param {boolean} createDelete Whether to propagate a message that this
    *                               Type was deleted.
    */
-  _delete (y, createDelete, gcChildren = true) {
+  _delete (y, createDelete, gcChildren) {
+    if (gcChildren === undefined) {
+      gcChildren = y._hasUndoManager === false
+    }
     super._delete(y, createDelete, gcChildren)
     y._transaction.changedTypes.delete(this)
     // delete map types
diff --git a/src/Util/UndoManager.js b/src/Util/UndoManager.js
index 54adbbde..0810ffc8 100644
--- a/src/Util/UndoManager.js
+++ b/src/Util/UndoManager.js
@@ -75,6 +75,7 @@ export default class UndoManager {
     this._lastTransactionWasUndo = false
     const y = scope._y
     this.y = y
+    y._hasUndoManager = true
     y.on('afterTransaction', (y, transaction, remote) => {
       if (!remote && transaction.changedParentTypes.has(scope)) {
         let reverseOperation = new ReverseOperation(y, transaction)
diff --git a/src/Y.js b/src/Y.js
index ca7b63ef..7a1ab318 100644
--- a/src/Y.js
+++ b/src/Y.js
@@ -79,6 +79,7 @@ export default class Y extends NamedEventHandler {
     }
     // for compatibility with isParentOf
     this._parent = null
+    this._hasUndoManager = false
   }
   _setContentReady () {
     if (!this._contentReady) {