diff --git a/Sources/VRCKit/Services/FavoriteService.swift b/Sources/VRCKit/Services/FavoriteService.swift
index 3244663..0d7a934 100644
--- a/Sources/VRCKit/Services/FavoriteService.swift
+++ b/Sources/VRCKit/Services/FavoriteService.swift
@@ -26,8 +26,9 @@ public final actor FavoriteService: APIService, FavoriteServiceProtocol {
     public func listFavorites(type: FavoriteType) async throws -> [Favorite] {
         try await withThrowingTaskGroup(of: [Favorite].self) { taskGroup in
             for offset in [0, 100, 200, 300] {
-                taskGroup.addTask { [unowned self] in
-                    try await listFavorites(n: 100, offset: offset, type: type)
+                taskGroup.addTask { [weak self] in
+                    guard let self = self else { return [] }
+                    return try await listFavorites(n: 100, offset: offset, type: type)
                 }
             }
             var results: [Favorite] = []
@@ -71,8 +72,14 @@ public final actor FavoriteService: APIService, FavoriteServiceProtocol {
     public func fetchFavoriteList(favoriteGroups: [FavoriteGroup], type: FavoriteType) async throws -> [FavoriteList] {
         try await withThrowingTaskGroup(of: FavoriteList.self) { taskGroup in
             for favoriteGroup in favoriteGroups.filter({ $0.type == type }) {
-                taskGroup.addTask { [unowned self] in
-                    FavoriteList(
+                taskGroup.addTask { [weak self] in
+                    guard let self = self else {
+                        return FavoriteList(
+                            id: favoriteGroup.id,
+                            favorites: []
+                        )
+                    }
+                    return FavoriteList(
                         id: favoriteGroup.id,
                         favorites: try await listFavorites(type: type, tag: favoriteGroup.name)
                     )
diff --git a/Sources/VRCKit/Services/WorldService.swift b/Sources/VRCKit/Services/WorldService.swift
index 7ef032e..55521b7 100644
--- a/Sources/VRCKit/Services/WorldService.swift
+++ b/Sources/VRCKit/Services/WorldService.swift
@@ -24,7 +24,8 @@ public final actor WorldService: APIService, WorldServiceProtocol {
     public func fetchFavoritedWorlds() async throws -> [FavoriteWorld] {
         try await withThrowingTaskGroup(of: FavoriteWorldsWithOffset.self) { taskGroup in
             for offset in Array(stride(from: 0, to: maxCount, by: limit)) {
-                taskGroup.addTask { [unowned self] in
+                taskGroup.addTask { [weak self] in
+                    guard let self = self else { return (offset, []) }
                     let worlds = try await fetchFavoritedWorlds(n: limit, offset: offset)
                     return (offset, worlds)
                 }