diff --git a/commonspace/object/tree/objecttree/change.go b/commonspace/object/tree/objecttree/change.go
index 635cb843..36eb3fe2 100644
--- a/commonspace/object/tree/objecttree/change.go
+++ b/commonspace/object/tree/objecttree/change.go
@@ -25,6 +25,7 @@ type Change struct {
 	Data        []byte
 	Model       interface{}
 	Signature   []byte
+	DataType    string
 
 	// iterator helpers
 	visited          bool
@@ -45,6 +46,7 @@ func NewChange(id string, identity crypto.PubKey, ch *treechangeproto.TreeChange
 		IsSnapshot:  ch.IsSnapshot,
 		Identity:    identity,
 		Signature:   signature,
+		DataType:    ch.DataType,
 	}
 }
 
diff --git a/commonspace/object/tree/objecttree/changebuilder.go b/commonspace/object/tree/objecttree/changebuilder.go
index 038ce528..a171b29f 100644
--- a/commonspace/object/tree/objecttree/changebuilder.go
+++ b/commonspace/object/tree/objecttree/changebuilder.go
@@ -20,6 +20,7 @@ type BuilderContent struct {
 	ReadKey        crypto.SymKey
 	Content        []byte
 	Timestamp      int64
+	DataType       string
 }
 
 type InitialContent struct {
@@ -169,6 +170,7 @@ func (c *changeBuilder) Build(payload BuilderContent) (ch *Change, rawIdChange *
 		Timestamp:      payload.Timestamp,
 		Identity:       identity,
 		IsSnapshot:     payload.IsSnapshot,
+		DataType:       payload.DataType,
 	}
 	if payload.ReadKey != nil {
 		var encrypted []byte
@@ -225,6 +227,7 @@ func (c *changeBuilder) Marshall(ch *Change) (raw *treechangeproto.RawTreeChange
 		Timestamp:      ch.Timestamp,
 		Identity:       identity,
 		IsSnapshot:     ch.IsSnapshot,
+		DataType:       ch.DataType,
 	}
 	var marshalled []byte
 	marshalled, err = treeChange.Marshal()
diff --git a/commonspace/object/tree/objecttree/objecttree.go b/commonspace/object/tree/objecttree/objecttree.go
index 4d099f51..4cd123a1 100644
--- a/commonspace/object/tree/objecttree/objecttree.go
+++ b/commonspace/object/tree/objecttree/objecttree.go
@@ -274,6 +274,7 @@ func (ot *objectTree) prepareBuilderContent(content SignableChangeContent) (cnt
 		PrivKey:        content.Key,
 		ReadKey:        readKey,
 		Content:        content.Data,
+		DataType:       content.DataType,
 		Timestamp:      timestamp,
 	}
 	return
diff --git a/commonspace/object/tree/objecttree/objecttree_test.go b/commonspace/object/tree/objecttree/objecttree_test.go
index 1ac1a844..3f241c9c 100644
--- a/commonspace/object/tree/objecttree/objecttree_test.go
+++ b/commonspace/object/tree/objecttree/objecttree_test.go
@@ -107,7 +107,7 @@ func TestObjectTree(t *testing.T) {
 		oTree, err := BuildObjectTree(store, aclList)
 		require.NoError(t, err)
 
-		t.Run("0 timestamp is changed to current", func(t *testing.T) {
+		t.Run("0 timestamp is changed to current, data type is correct", func(t *testing.T) {
 			start := time.Now()
 			res, err := oTree.AddContent(ctx, SignableChangeContent{
 				Data:        []byte("some"),
@@ -115,6 +115,7 @@ func TestObjectTree(t *testing.T) {
 				IsSnapshot:  false,
 				IsEncrypted: true,
 				Timestamp:   0,
+				DataType:    mockDataType,
 			})
 			end := time.Now()
 			require.NoError(t, err)
@@ -125,6 +126,7 @@ func TestObjectTree(t *testing.T) {
 			require.GreaterOrEqual(t, start.Unix(), ch.Timestamp)
 			require.LessOrEqual(t, end.Unix(), ch.Timestamp)
 			require.Equal(t, res.Added[0].Id, oTree.(*objectTree).tree.lastIteratedHeadId)
+			require.Equal(t, mockDataType, ch.DataType)
 		})
 		t.Run("timestamp is set correctly", func(t *testing.T) {
 			someTs := time.Now().Add(time.Hour).Unix()
@@ -174,6 +176,9 @@ func TestObjectTree(t *testing.T) {
 		// check tree iterate
 		var iterChangesId []string
 		err = objTree.IterateRoot(nil, func(change *Change) bool {
+			if change.Id != objTree.Id() {
+				assert.Equal(t, mockDataType, change.DataType)
+			}
 			iterChangesId = append(iterChangesId, change.Id)
 			return true
 		})
@@ -575,6 +580,12 @@ func TestObjectTree(t *testing.T) {
 				_, ok := changeIds[id]
 				assert.Equal(t, false, ok)
 			}
+
+			for _, rawCh := range changes {
+				ch, err := ctx.objTree.(*objectTree).changeBuilder.Unmarshall(rawCh, false)
+				require.NoError(t, err)
+				require.Equal(t, mockDataType, ch.DataType)
+			}
 		})
 
 		t.Run("changes from tree after 5", func(t *testing.T) {
diff --git a/commonspace/object/tree/objecttree/signablecontent.go b/commonspace/object/tree/objecttree/signablecontent.go
index b16890b5..306d58aa 100644
--- a/commonspace/object/tree/objecttree/signablecontent.go
+++ b/commonspace/object/tree/objecttree/signablecontent.go
@@ -16,4 +16,6 @@ type SignableChangeContent struct {
 	IsEncrypted bool
 	// Timestamp is a timestamp of change, if it is <= 0, then we use current timestamp
 	Timestamp int64
+	// DataType contains additional info about the data in the payload
+	DataType string
 }
diff --git a/commonspace/object/tree/objecttree/testutils.go b/commonspace/object/tree/objecttree/testutils.go
index adb20349..997b1ae3 100644
--- a/commonspace/object/tree/objecttree/testutils.go
+++ b/commonspace/object/tree/objecttree/testutils.go
@@ -11,7 +11,10 @@ import (
 type mockPubKey struct {
 }
 
-const mockKeyValue = "mockKey"
+const (
+	mockKeyValue = "mockKey"
+	mockDataType = "mockDataType"
+)
 
 func (m mockPubKey) Equals(key crypto.Key) bool {
 	return true
@@ -99,6 +102,7 @@ func (c *MockChangeCreator) CreateRawWithData(id, aclId, snapshotId string, isSn
 		SnapshotBaseId: snapshotId,
 		ChangesData:    data,
 		IsSnapshot:     isSnapshot,
+		DataType:       mockDataType,
 	}
 	res, _ := aclChange.Marshal()
 
diff --git a/commonspace/object/tree/treechangeproto/protos/treechange.proto b/commonspace/object/tree/treechangeproto/protos/treechange.proto
index eb331567..cd03aba9 100644
--- a/commonspace/object/tree/treechangeproto/protos/treechange.proto
+++ b/commonspace/object/tree/treechangeproto/protos/treechange.proto
@@ -38,6 +38,8 @@ message TreeChange {
   bytes identity = 7;
   // IsSnapshot indicates whether this change contains a snapshot of state
   bool isSnapshot = 8;
+  // DataType indicates some special parameters of data for the client
+  string dataType = 9;
 }
 
 // RawTreeChange is a marshalled TreeChange (or RootChange) payload and a signature of this payload
diff --git a/commonspace/object/tree/treechangeproto/treechange.pb.go b/commonspace/object/tree/treechangeproto/treechange.pb.go
index 34d57487..2af38c2b 100644
--- a/commonspace/object/tree/treechangeproto/treechange.pb.go
+++ b/commonspace/object/tree/treechangeproto/treechange.pb.go
@@ -171,6 +171,8 @@ type TreeChange struct {
 	Identity []byte `protobuf:"bytes,7,opt,name=identity,proto3" json:"identity,omitempty"`
 	// IsSnapshot indicates whether this change contains a snapshot of state
 	IsSnapshot bool `protobuf:"varint,8,opt,name=isSnapshot,proto3" json:"isSnapshot,omitempty"`
+	// DataType indicates some special parameters of data for the client
+	DataType string `protobuf:"bytes,9,opt,name=dataType,proto3" json:"dataType,omitempty"`
 }
 
 func (m *TreeChange) Reset()         { *m = TreeChange{} }
@@ -262,6 +264,13 @@ func (m *TreeChange) GetIsSnapshot() bool {
 	return false
 }
 
+func (m *TreeChange) GetDataType() string {
+	if m != nil {
+		return m.DataType
+	}
+	return ""
+}
+
 // RawTreeChange is a marshalled TreeChange (or RootChange) payload and a signature of this payload
 type RawTreeChange struct {
 	// Payload is a byte payload containing TreeChange
@@ -846,54 +855,55 @@ func init() {
 }
 
 var fileDescriptor_5033f0301ef9b772 = []byte{
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+	0xc8, 0xb2, 0x00, 0x7a, 0x08, 0x90, 0xcc, 0x37, 0xb9, 0xaa, 0xd3, 0x38, 0xf8, 0x32, 0x1f, 0xbe,
+	0x82, 0x32, 0xcb, 0x85, 0xb8, 0xef, 0x4d, 0xd8, 0x59, 0x55, 0x82, 0xfe, 0x08, 0x30, 0x44, 0xee,
+	0x5f, 0xc5, 0x3e, 0x97, 0x38, 0x23, 0xb6, 0x5b, 0x26, 0xd6, 0x9b, 0x7b, 0xf4, 0x0c, 0x96, 0xf3,
+	0xa7, 0x67, 0xb0, 0x35, 0x98, 0x8c, 0x46, 0x69, 0x56, 0x86, 0x7f, 0x4e, 0x50, 0xc8, 0x55, 0xe4,
+	0xd2, 0x14, 0x27, 0x45, 0xb7, 0x9e, 0xc1, 0xca, 0x91, 0xf4, 0x57, 0x68, 0x2f, 0x20, 0x11, 0x47,
+	0xa1, 0xd0, 0x27, 0x71, 0x85, 0x52, 0x27, 0x25, 0xbf, 0x9e, 0xc1, 0x96, 0x62, 0xe9, 0x31, 0x6c,
+	0x62, 0x92, 0x44, 0xc9, 0x3c, 0x59, 0x55, 0x25, 0xfb, 0xa2, 0x9c, 0xec, 0x38, 0xef, 0xd4, 0x33,
+	0x58, 0x31, 0xea, 0xa8, 0x06, 0x6b, 0x7f, 0xa5, 0x52, 0xb9, 0xff, 0x10, 0x68, 0x15, 0xd5, 0xa0,
+	0x3b, 0xb0, 0x96, 0xaa, 0x91, 0x9d, 0x46, 0x6d, 0xd0, 0xef, 0xa1, 0x36, 0x3b, 0x2e, 0x96, 0xe9,
+	0x54, 0x5e, 0x33, 0xaa, 0xcc, 0x9f, 0xba, 0xd0, 0xcc, 0x8e, 0xe3, 0x39, 0x97, 0x43, 0xab, 0xa2,
+	0xf2, 0x16, 0x30, 0xf7, 0x5f, 0x02, 0xdb, 0x2b, 0x24, 0x7d, 0x1b, 0x32, 0xff, 0x11, 0xbd, 0xb1,
+	0xca, 0x13, 0x79, 0x1b, 0x36, 0x5d, 0xf8, 0x6c, 0x69, 0xa2, 0x29, 0x13, 0x35, 0xd1, 0xd9, 0x7b,
+	0xa0, 0x8d, 0xf4, 0x7e, 0xc0, 0x24, 0xe9, 0x46, 0xbe, 0x3e, 0x4f, 0x55, 0x96, 0x99, 0xee, 0xb5,
+	0x1e, 0xb3, 0x66, 0xd1, 0x0f, 0x07, 0x51, 0xe9, 0x75, 0x20, 0x4b, 0xaf, 0xc3, 0xd2, 0x7d, 0x6e,
+	0xae, 0xb8, 0xcf, 0xbf, 0xbd, 0x01, 0x50, 0xc4, 0xd2, 0x22, 0x82, 0xb6, 0x00, 0xae, 0x42, 0xfc,
+	0x3b, 0x46, 0x4f, 0xa2, 0xdf, 0x36, 0x68, 0x1b, 0x9a, 0xa7, 0x28, 0xe7, 0xec, 0xdb, 0x84, 0x5a,
+	0xb0, 0x53, 0x1a, 0xb1, 0x5e, 0x31, 0x69, 0x1b, 0x1a, 0xea, 0xf3, 0xb7, 0xc1, 0x40, 0xa0, 0x6c,
+	0x3f, 0x54, 0x8e, 0x7e, 0xfa, 0xf0, 0x6c, 0x93, 0xc7, 0x67, 0x9b, 0x7c, 0x7c, 0xb6, 0xc9, 0xc3,
+	0x8b, 0x6d, 0x3c, 0xbe, 0xd8, 0xc6, 0xd3, 0x8b, 0x6d, 0xdc, 0x7c, 0xf3, 0xca, 0xd7, 0xf6, 0x76,
+	0x5d, 0xfd, 0x7d, 0xf7, 0x29, 0x00, 0x00, 0xff, 0xff, 0xb0, 0xa9, 0x1c, 0xd8, 0x9f, 0x07, 0x00,
+	0x00,
 }
 
 func (m *RootChange) Marshal() (dAtA []byte, err error) {
@@ -986,6 +996,13 @@ func (m *TreeChange) MarshalToSizedBuffer(dAtA []byte) (int, error) {
 	_ = i
 	var l int
 	_ = l
+	if len(m.DataType) > 0 {
+		i -= len(m.DataType)
+		copy(dAtA[i:], m.DataType)
+		i = encodeVarintTreechange(dAtA, i, uint64(len(m.DataType)))
+		i--
+		dAtA[i] = 0x4a
+	}
 	if m.IsSnapshot {
 		i--
 		if m.IsSnapshot {
@@ -1607,6 +1624,10 @@ func (m *TreeChange) Size() (n int) {
 	if m.IsSnapshot {
 		n += 2
 	}
+	l = len(m.DataType)
+	if l > 0 {
+		n += 1 + l + sovTreechange(uint64(l))
+	}
 	return n
 }
 
@@ -2372,6 +2393,38 @@ func (m *TreeChange) Unmarshal(dAtA []byte) error {
 				}
 			}
 			m.IsSnapshot = bool(v != 0)
+		case 9:
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field DataType", wireType)
+			}
+			var stringLen uint64
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowTreechange
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				stringLen |= uint64(b&0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			intStringLen := int(stringLen)
+			if intStringLen < 0 {
+				return ErrInvalidLengthTreechange
+			}
+			postIndex := iNdEx + intStringLen
+			if postIndex < 0 {
+				return ErrInvalidLengthTreechange
+			}
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			m.DataType = string(dAtA[iNdEx:postIndex])
+			iNdEx = postIndex
 		default:
 			iNdEx = preIndex
 			skippy, err := skipTreechange(dAtA[iNdEx:])
diff --git a/commonspace/syncstatus/syncstatus.go b/commonspace/syncstatus/syncstatus.go
index 9c580fe6..4eabfb31 100644
--- a/commonspace/syncstatus/syncstatus.go
+++ b/commonspace/syncstatus/syncstatus.go
@@ -290,6 +290,9 @@ func (s *syncStatusService) RemoveAllExcept(senderId string, differentRemoteIds
 }
 
 func (s *syncStatusService) Close(ctx context.Context) error {
+	if s.periodicSync == nil {
+		return nil
+	}
 	s.periodicSync.Close()
 	return nil
 }