diff --git a/packages/backend/test-federation/test/user.test.ts b/packages/backend/test-federation/test/user.test.ts
index 83dcb8df44..ee69e857bc 100644
--- a/packages/backend/test-federation/test/user.test.ts
+++ b/packages/backend/test-federation/test/user.test.ts
@@ -381,7 +381,8 @@ describe('User', () => {
 
 				await alice.client.request('i/delete-account', { password: alice.password });
 				// NOTE: user deletion query is slow
-				await sleep(4000);
+				// FIXME: ensure user is removed successfully
+				await sleep(10000);
 
 				const following = await bob.client.request('users/following', { userId: bob.id });
 				strictEqual(following.length, 0); // no following relation
@@ -480,7 +481,8 @@ describe('User', () => {
 
 				await aAdmin.client.request('admin/suspend-user', { userId: alice.id });
 				// NOTE: user deletion query is slow
-				await sleep(4000);
+				// FIXME: ensure user is removed successfully
+				await sleep(10000);
 
 				const following = await bob.client.request('users/following', { userId: bob.id });
 				strictEqual(following.length, 0); // no following relation
diff --git a/packages/sw/src/scripts/create-notification.ts b/packages/sw/src/scripts/create-notification.ts
index 77b3f88791..783c78f7dc 100644
--- a/packages/sw/src/scripts/create-notification.ts
+++ b/packages/sw/src/scripts/create-notification.ts
@@ -271,7 +271,7 @@ async function composeNotification(data: PushNotificationDataMap[keyof PushNotif
 		case 'newChatMessage':
 			if (data.body.toRoom != null) {
 				return [`${data.body.toRoom.name}: ${getUserName(data.body.fromUser)}: ${data.body.text}`, {
-					icon: data.body.fromUser.avatarUrl,
+					icon: data.body.fromUser.avatarUrl ?? undefined,
 					badge: iconUrl('messages'),
 					tag: `chat:room:${data.body.toRoomId}`,
 					data,
@@ -279,7 +279,7 @@ async function composeNotification(data: PushNotificationDataMap[keyof PushNotif
 				}];
 			} else {
 				return [`${getUserName(data.body.fromUser)}: ${data.body.text}`, {
-					icon: data.body.fromUser.avatarUrl,
+					icon: data.body.fromUser.avatarUrl ?? undefined,
 					badge: iconUrl('messages'),
 					tag: `chat:user:${data.body.fromUserId}`,
 					data,