diff --git a/plugins/notifications-backend-module-slack/src/lib/SlackNotificationProcessor.test.ts b/plugins/notifications-backend-module-slack/src/lib/SlackNotificationProcessor.test.ts
index c970aec7ba..ad4bf01e9f 100644
--- a/plugins/notifications-backend-module-slack/src/lib/SlackNotificationProcessor.test.ts
+++ b/plugins/notifications-backend-module-slack/src/lib/SlackNotificationProcessor.test.ts
@@ -829,7 +829,7 @@ describe('SlackNotificationProcessor', () => {
 
       const calls = (slack.chat.postMessage as jest.Mock).mock.calls;
       expect(calls).toHaveLength(1);
-      expect(calls[0][0]).not.toHaveProperty('username');
+      expect(calls[0][0].username).toBeUndefined();
     });
   });
 
diff --git a/plugins/notifications-backend-module-slack/src/lib/util.ts b/plugins/notifications-backend-module-slack/src/lib/util.ts
index 1116218b09..33293ea24f 100644
--- a/plugins/notifications-backend-module-slack/src/lib/util.ts
+++ b/plugins/notifications-backend-module-slack/src/lib/util.ts
@@ -30,7 +30,7 @@ export function toChatPostMessageArgs(options: {
   const args: ChatPostMessageArguments = {
     channel,
     text: payload.title,
-    ...(username && { username }),
+    username,
     attachments: [
       {
         color: getColor(payload.severity),