diff --git a/zerver/lib/slack_data_to_zulip_data.py b/zerver/lib/slack_data_to_zulip_data.py
index 4df1d6475d..e38f0d6573 100755
--- a/zerver/lib/slack_data_to_zulip_data.py
+++ b/zerver/lib/slack_data_to_zulip_data.py
@@ -600,7 +600,7 @@ def channel_message_to_zerver_message(REALM_ID: int, users: List[ZerverFieldsT],
         zerver_message.append(zulip_message)
 
         # construct usermessages
-        zerver_usermessage, usermessage_id_count = build_zerver_usermessage(
+        usermessage_id_count = build_zerver_usermessage(
             zerver_usermessage, usermessage_id_count, usermessage_id_list,
             zerver_subscription, recipient_id, mentioned_users_id, message_id)
 
@@ -617,8 +617,7 @@ def get_message_sending_user(message: ZerverFieldsT) -> str:
 def build_zerver_usermessage(zerver_usermessage: List[ZerverFieldsT], usermessage_id_count: int,
                              usermessage_id_list: List[int],
                              zerver_subscription: List[ZerverFieldsT], recipient_id: int,
-                             mentioned_users_id: List[int],
-                             message_id: int) -> Tuple[List[ZerverFieldsT], int]:
+                             mentioned_users_id: List[int], message_id: int) -> int:
     for subscription in zerver_subscription:
         if subscription['recipient'] == recipient_id:
             flags_mask = 1  # For read
@@ -632,7 +631,7 @@ def build_zerver_usermessage(zerver_usermessage: List[ZerverFieldsT], usermessag
                 message=message_id)
             usermessage_id_count += 1
             zerver_usermessage.append(usermessage)
-    return zerver_usermessage, usermessage_id_count
+    return usermessage_id_count
 
 def do_convert_data(slack_zip_file: str, realm_subdomain: str, output_dir: str, token: str) -> None:
     check_subdomain_available(realm_subdomain)
diff --git a/zerver/tests/test_slack_importer.py b/zerver/tests/test_slack_importer.py
index 76f059da2f..ec836010a8 100644
--- a/zerver/tests/test_slack_importer.py
+++ b/zerver/tests/test_slack_importer.py
@@ -392,25 +392,21 @@ class SlackImporter(ZulipTestCase):
         mentioned_users_id = [12, 3, 16]
         message_id = 9
 
-        test_zerver_usermessage, test_usermessage_id = build_zerver_usermessage(zerver_usermessage,
-                                                                                usermessage_id_count,
-                                                                                usermessage_id_list,
-                                                                                zerver_subscription,
-                                                                                recipient_id,
-                                                                                mentioned_users_id,
-                                                                                message_id)
+        test_usermessage_id = build_zerver_usermessage(zerver_usermessage, usermessage_id_count,
+                                                       usermessage_id_list, zerver_subscription,
+                                                       recipient_id, mentioned_users_id, message_id)
         self.assertEqual(test_usermessage_id, 4)
 
-        self.assertEqual(test_zerver_usermessage[0]['flags_mask'], 1)
-        self.assertEqual(test_zerver_usermessage[0]['id'], 3)
-        self.assertEqual(test_zerver_usermessage[0]['message'], message_id)
-        self.assertEqual(test_zerver_usermessage[1]['user_profile'],
+        self.assertEqual(zerver_usermessage[0]['flags_mask'], 1)
+        self.assertEqual(zerver_usermessage[0]['id'], 3)
+        self.assertEqual(zerver_usermessage[0]['message'], message_id)
+        self.assertEqual(zerver_usermessage[1]['user_profile'],
                          zerver_subscription[2]['user_profile'])
-        self.assertEqual(test_zerver_usermessage[1]['flags_mask'], 9)
-        self.assertEqual(test_zerver_usermessage[3]['id'], 11)
-        self.assertEqual(test_zerver_usermessage[3]['message'], message_id)
+        self.assertEqual(zerver_usermessage[1]['flags_mask'], 9)
+        self.assertEqual(zerver_usermessage[3]['id'], 11)
+        self.assertEqual(zerver_usermessage[3]['message'], message_id)
 
-    @mock.patch("zerver.lib.slack_data_to_zulip_data.build_zerver_usermessage", return_value = [[], 2])
+    @mock.patch("zerver.lib.slack_data_to_zulip_data.build_zerver_usermessage", return_value = 2)
     def test_channel_message_to_zerver_message(self, mock_build_zerver_usermessage: mock.Mock) -> None:
 
         user_data = [{"id": "U066MTL5U", "name": "john doe", "deleted": False, "real_name": "John"},