diff --git a/CHANGELOG.md b/CHANGELOG.md
index 34d4d4ad..5c1adf80 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,8 +3,8 @@
 * 支持gcm推送点击
 
 ## 3.8.3+2
-增加群组已读回执；
-不在提供EMContact类，直接返回String类型username;
+* 增加群组已读回执；
+* 不在提供EMContact类，直接返回String类型username;
 
 ## 3.8.3
 * 增加用户属性；
diff --git a/ios/Classes/EMMessage+Flutter.m b/ios/Classes/EMMessage+Flutter.m
index 099c4ffa..678bb0ed 100644
--- a/ios/Classes/EMMessage+Flutter.m
+++ b/ios/Classes/EMMessage+Flutter.m
@@ -49,6 +49,8 @@ + (EMMessage *)fromJson:(NSDictionary *)aJson
     msg.isDeliverAcked = [aJson[@"hasDeliverAck"] boolValue];
     msg.isRead = [aJson[@"hasRead"] boolValue];
     msg.isNeedGroupAck = [aJson[@"needGroupAck"] boolValue];
+    // read only
+    // msg.groupAckCount = [aJson[@"groupAckCount"] intValue]
     msg.ext = aJson[@"attributes"];
     return msg;
 }
@@ -65,6 +67,7 @@ - (NSDictionary *)toJson
     ret[@"hasReadAck"] = @(self.isReadAcked);
     ret[@"needGroupAck"] = @(self.isNeedGroupAck);
     ret[@"serverTime"] = @(self.timestamp);
+    ret[@"groupAckCount"] = @(self.groupAckCount);
     ret[@"attributes"] = self.ext ?: @{};
     ret[@"localTime"] = @(self.localTime);
     ret[@"status"] = @([self statusToInt:self.status]);
diff --git a/lib/src/em_chat_room_manager.dart b/lib/src/em_chat_room_manager.dart
index a094e144..9f4fcec9 100644
--- a/lib/src/em_chat_room_manager.dart
+++ b/lib/src/em_chat_room_manager.dart
@@ -220,7 +220,7 @@ class EMChatRoomManager {
   }
 
   /// @nodoc 获取聊天室成员列表，[roomId] [cursor] [pageSize]
-  Future<EMCursorResult<EMChatRoom>> fetchChatRoomMembers(
+  Future<EMCursorResult<String?>> fetchChatRoomMembers(
     String roomId, {
     String cursor = '',
     int pageSize = 200,
@@ -229,7 +229,7 @@ class EMChatRoomManager {
     Map result =
         await _channel.invokeMethod(EMSDKMethod.fetchChatRoomMembers, req);
     EMError.hasErrorFromResult(result);
-    return EMCursorResult<EMChatRoom>.fromJson(
+    return EMCursorResult<String?>.fromJson(
         result[EMSDKMethod.fetchChatRoomMembers],
         dataItemCallback: (obj) => obj);
   }
diff --git a/lib/src/models/em_message.dart b/lib/src/models/em_message.dart
index 14f11277..88a8a271 100644
--- a/lib/src/models/em_message.dart
+++ b/lib/src/models/em_message.dart
@@ -394,7 +394,7 @@ class EMMessage {
       ..hasRead = map.boolValue('hasRead')
       ..hasReadAck = map.boolValue('hasReadAck')
       ..needGroupAck = map.boolValue('needGroupAck')
-      ..groupAckCount = map["groupAckCount"] as int
+      ..groupAckCount = map["groupAckCount"] as int? ?? 0
       ..hasDeliverAck = map.boolValue('hasDeliverAck')
       .._msgId = map['msgId'] as String?
       ..conversationId = map['conversationId'] as String?