diff --git a/src/services/chat_service/chat_service.js b/src/services/chat_service/chat_service.js
index b0905dc1..1fc4e390 100644
--- a/src/services/chat_service/chat_service.js
+++ b/src/services/chat_service/chat_service.js
@@ -6,7 +6,7 @@ const empty = (chatId) => {
     idempotencyKeyIndex: {},
     messages: [],
     newMessageCount: 0,
-    lastSeenTimestamp: 0,
+    lastSeenMessageId: '0',
     chatId: chatId,
     minId: undefined,
     maxId: undefined
@@ -27,7 +27,7 @@ const clear = (storage) => {
 
   storage.messages = storage.messages.filter(m => failedMessageIds.includes(m.id))
   storage.newMessageCount = 0
-  storage.lastSeenTimestamp = 0
+  storage.lastSeenMessageId = '0'
   storage.minId = undefined
   storage.maxId = undefined
 }
@@ -104,7 +104,7 @@ const add = (storage, { messages: newMessages, updateMaxId = true }) => {
     }
 
     if (!storage.idIndex[message.id] && !isConfirmation(storage, message)) {
-      if (storage.lastSeenTimestamp < message.created_at) {
+      if (storage.lastSeenMessageId < message.id) {
         storage.newMessageCount++
       }
       storage.idIndex[message.id] = message
@@ -122,7 +122,7 @@ const isConfirmation = (storage, message) => {
 const resetNewMessageCount = (storage) => {
   if (!storage) { return }
   storage.newMessageCount = 0
-  storage.lastSeenTimestamp = new Date()
+  storage.lastSeenMessageId = storage.maxId
 }
 
 // Inserts date separators and marks the head and tail if it's the chain of messages made by the same user
diff --git a/test/unit/specs/services/chat_service/chat_service.spec.js b/test/unit/specs/services/chat_service/chat_service.spec.js
index 15e64bb5..0251cae7 100644
--- a/test/unit/specs/services/chat_service/chat_service.spec.js
+++ b/test/unit/specs/services/chat_service/chat_service.spec.js
@@ -47,10 +47,10 @@ describe('chatService', () => {
 
       chatService.resetNewMessageCount(chat)
       expect(chat.newMessageCount).to.eql(0)
+      expect(chat.lastSeenMessageId).to.eql(message2.id)
 
-      const createdAt = new Date()
-      createdAt.setSeconds(createdAt.getSeconds() + 10)
-      chatService.add(chat, { messages: [ { message3, created_at: createdAt } ] })
+      // Add message with higher id
+      chatService.add(chat, { messages: [ message3 ] })
       expect(chat.newMessageCount).to.eql(1)
     })
   })