diff --git a/plugins/chat/app/models/chat/null_message.rb b/plugins/chat/app/models/chat/null_message.rb
index 44a92fad60c..2815d970c3d 100644
--- a/plugins/chat/app/models/chat/null_message.rb
+++ b/plugins/chat/app/models/chat/null_message.rb
@@ -6,7 +6,7 @@ module Chat
       nil
     end
 
-    def excerpt(max_length: nil)
+    def build_excerpt
       nil
     end
 
diff --git a/plugins/chat/app/serializers/chat/thread_original_message_serializer.rb b/plugins/chat/app/serializers/chat/thread_original_message_serializer.rb
index 9fda1a0946f..1e1bbab3653 100644
--- a/plugins/chat/app/serializers/chat/thread_original_message_serializer.rb
+++ b/plugins/chat/app/serializers/chat/thread_original_message_serializer.rb
@@ -12,6 +12,10 @@ module Chat
                :mentioned_users,
                :user
 
+    def excerpt
+      object.excerpt || object.build_excerpt
+    end
+
     def mentioned_users
       object
         .user_mentions
diff --git a/plugins/chat/app/serializers/chat/thread_preview_serializer.rb b/plugins/chat/app/serializers/chat/thread_preview_serializer.rb
index 65ba953c4e3..3a5c5db7f52 100644
--- a/plugins/chat/app/serializers/chat/thread_preview_serializer.rb
+++ b/plugins/chat/app/serializers/chat/thread_preview_serializer.rb
@@ -28,7 +28,7 @@ module Chat
     end
 
     def last_reply_excerpt
-      object.last_message.excerpt
+      object.last_message.excerpt || object.last_message.build_excerpt
     end
 
     def last_reply_user
diff --git a/plugins/chat/spec/models/chat/null_message_spec.rb b/plugins/chat/spec/models/chat/null_message_spec.rb
index 0a3b92425e2..65efc5cecc8 100644
--- a/plugins/chat/spec/models/chat/null_message_spec.rb
+++ b/plugins/chat/spec/models/chat/null_message_spec.rb
@@ -9,9 +9,9 @@ describe Chat::NullMessage do
     end
   end
 
-  describe "#excerpt" do
+  describe "#build_excerpt" do
     it "returns nil" do
-      expect(null_message.excerpt(max_length: 1)).to be_nil
+      expect(null_message.build_excerpt).to be_nil
     end
   end
 
diff --git a/plugins/chat/spec/system/message_thread_indicator_spec.rb b/plugins/chat/spec/system/message_thread_indicator_spec.rb
index 60a62473b96..2d8a4ea06a9 100644
--- a/plugins/chat/spec/system/message_thread_indicator_spec.rb
+++ b/plugins/chat/spec/system/message_thread_indicator_spec.rb
@@ -137,6 +137,15 @@ describe "Thread indicator for chat messages", type: :system do
       ).to have_content(thread_excerpt(thread_1.last_message.reload))
     end
 
+    it "builds an excerpt for the last reply if it doesn’t have one" do
+      thread_1.last_message.update!(excerpt: nil)
+      chat_page.visit_channel(channel)
+
+      expect(
+        channel_page.message_thread_indicator(thread_1.original_message).excerpt,
+      ).to have_content(thread_1.last_message.build_excerpt)
+    end
+
     it "updates the last reply excerpt and participants when a new message is added to the thread" do
       new_user = Fabricate(:user)
       chat_system_user_bootstrap(user: new_user, channel: channel)
diff --git a/plugins/chat/spec/system/thread_list/full_page_spec.rb b/plugins/chat/spec/system/thread_list/full_page_spec.rb
index 4a719666bd7..03072d857a4 100644
--- a/plugins/chat/spec/system/thread_list/full_page_spec.rb
+++ b/plugins/chat/spec/system/thread_list/full_page_spec.rb
@@ -111,6 +111,15 @@ describe "Thread list in side panel | full page", type: :system do
       )
     end
 
+    it "builds an excerpt for the original message if it doesn’t have one" do
+      thread_1.original_message.update!(excerpt: nil)
+      chat_page.visit_threads_list(channel)
+
+      expect(thread_list_page.item_by_id(thread_1.id)).to have_content(
+        thread_1.original_message.build_excerpt,
+      )
+    end
+
     it "doesn’t show the thread original message user avatar" do
       chat_page.visit_threads_list(channel)