diff --git a/Sources/Model/User Interface/Renderable/RenderableStorage.swift b/Sources/Model/User Interface/Renderable/RenderableStorage.swift
index c8b880a..f152457 100644
--- a/Sources/Model/User Interface/Renderable/RenderableStorage.swift	
+++ b/Sources/Model/User Interface/Renderable/RenderableStorage.swift	
@@ -6,7 +6,7 @@
 //
 
 /// Store a reference to a rendered view in a view storage.
-public class RenderableStorage {
+public actor RenderableStorage {
 
     /// The pointer.
     ///
diff --git a/Sources/View/AppearObserver.swift b/Sources/View/AppearObserver.swift
index ba65acb..a2f3f3b 100644
--- a/Sources/View/AppearObserver.swift
+++ b/Sources/View/AppearObserver.swift
@@ -18,7 +18,7 @@ struct AppearObserver: ConvenienceWidget {
     ///     - modifiers: Modify views before being updated.
     ///     - type: The type of the app storage.
     func container<Storage>(
-        modifiers: [(any AnyView) -> any AnyView],
+        modifiers: [@Sendable (any AnyView) -> any AnyView],
         type: Storage.Type
     ) -> ViewStorage where Storage: AppStorage {
         let storage = content.storage(modifiers: modifiers, type: type)
@@ -34,7 +34,7 @@ struct AppearObserver: ConvenienceWidget {
     ///     - type: The type of the app storage.
     func update<Storage>(
         _ storage: ViewStorage,
-        modifiers: [(any AnyView) -> any AnyView],
+        modifiers: [@Sendable (any AnyView) -> any AnyView],
         updateProperties: Bool,
         type: Storage.Type
     ) where Storage: AppStorage {
diff --git a/Sources/View/ContentModifier.swift b/Sources/View/ContentModifier.swift
index 42acd8d..baad4fe 100644
--- a/Sources/View/ContentModifier.swift
+++ b/Sources/View/ContentModifier.swift
@@ -18,7 +18,7 @@ struct ContentModifier<Content>: ConvenienceWidget where Content: AnyView {
     ///     - modifiers: Modify views before being updated.
     ///     - type: The type of the app storage.
     func container<Storage>(
-        modifiers: [(any AnyView) -> any AnyView],
+        modifiers: [@Sendable (any AnyView) -> any AnyView],
         type: Storage.Type
     ) -> ViewStorage where Storage: AppStorage {
         content.storage(modifiers: modifiers + [modifyView], type: type)
@@ -32,7 +32,7 @@ struct ContentModifier<Content>: ConvenienceWidget where Content: AnyView {
     ///     - type: The type of the app storage.
     func update<Storage>(
         _ storage: ViewStorage,
-        modifiers: [(any AnyView) -> any AnyView],
+        modifiers: [@Sendable (any AnyView) -> any AnyView],
         updateProperties: Bool,
         type: Storage.Type
     ) where Storage: AppStorage {
@@ -42,7 +42,7 @@ struct ContentModifier<Content>: ConvenienceWidget where Content: AnyView {
 
     /// Apply the modifier to a view.
     /// - Parameter view: The view.
-    func modifyView(_ view: AnyView) -> AnyView {
+    @Sendable func modifyView(_ view: AnyView) -> AnyView {
         if let view = view as? Content {
             return modify(view).stopModifiers()
         } else {
diff --git a/Sources/View/Freeze.swift b/Sources/View/Freeze.swift
index 15b0ad9..927baf4 100644
--- a/Sources/View/Freeze.swift
+++ b/Sources/View/Freeze.swift
@@ -18,7 +18,7 @@ struct Freeze: ConvenienceWidget {
     ///     - modifiers: Modify views before being updated.
     ///     - type: The type of the app storage.
     func container<Storage>(
-        modifiers: [(any AnyView) -> any AnyView],
+        modifiers: [@Sendable (any AnyView) -> any AnyView],
         type: Storage.Type
     ) -> ViewStorage where Storage: AppStorage {
         content.storage(modifiers: modifiers, type: type)
@@ -32,7 +32,7 @@ struct Freeze: ConvenienceWidget {
     ///     - type: The type of the app storage.
     func update<Storage>(
         _ storage: ViewStorage,
-        modifiers: [(any AnyView) -> any AnyView],
+        modifiers: [@Sendable (any AnyView) -> any AnyView],
         updateProperties: Bool,
         type: Storage.Type
     ) where Storage: AppStorage {
diff --git a/Sources/View/InspectorWrapper.swift b/Sources/View/InspectorWrapper.swift
index 347d713..b09c6c7 100644
--- a/Sources/View/InspectorWrapper.swift
+++ b/Sources/View/InspectorWrapper.swift
@@ -18,7 +18,7 @@ struct InspectorWrapper: ConvenienceWidget {
     ///     - modifiers: Modify views before being updated.
     ///     - type: The type of the app storage.
     func container<Storage>(
-        modifiers: [(any AnyView) -> any AnyView],
+        modifiers: [@Sendable (any AnyView) -> any AnyView],
         type: Storage.Type
     ) -> ViewStorage where Storage: AppStorage {
         let storage = content.storage(modifiers: modifiers, type: type)
@@ -34,7 +34,7 @@ struct InspectorWrapper: ConvenienceWidget {
     ///     - type: The type of the app storage.
     func update<Storage>(
         _ storage: ViewStorage,
-        modifiers: [(any AnyView) -> any AnyView],
+        modifiers: [@Sendable (any AnyView) -> any AnyView],
         updateProperties: Bool,
         type: Storage.Type
     ) where Storage: AppStorage {
diff --git a/Sources/View/ModifierStopper.swift b/Sources/View/ModifierStopper.swift
index 32834fe..d5ec0bc 100644
--- a/Sources/View/ModifierStopper.swift
+++ b/Sources/View/ModifierStopper.swift
@@ -16,7 +16,7 @@ struct ModifierStopper: ConvenienceWidget {
     ///     - modifiers: Modify views before being updated.
     ///     - type: The type of the app storage.
     func container<Storage>(
-        modifiers: [(any AnyView) -> any AnyView],
+        modifiers: [@Sendable (any AnyView) -> any AnyView],
         type: Storage.Type
     ) -> ViewStorage where Storage: AppStorage {
         content.storage(modifiers: [], type: type)
@@ -30,7 +30,7 @@ struct ModifierStopper: ConvenienceWidget {
     ///     - type: The type of the app storage.
     func update<Storage>(
         _ storage: ViewStorage,
-        modifiers: [(any AnyView) -> any AnyView],
+        modifiers: [@Sendable (any AnyView) -> any AnyView],
         updateProperties: Bool,
         type: Storage.Type
     ) where Storage: AppStorage {
diff --git a/Tests/SampleBackends/Backend1.swift b/Tests/SampleBackends/Backend1.swift
index ab769dd..cb48573 100644
--- a/Tests/SampleBackends/Backend1.swift
+++ b/Tests/SampleBackends/Backend1.swift
@@ -56,7 +56,7 @@ public enum Backend1 {
             self.action = action
         }
 
-        public func container<Storage>(modifiers: [(any AnyView) -> any AnyView], type: Storage.Type) -> ViewStorage where Storage: AppStorage {
+        public func container<Storage>(modifiers: [@Sendable (any AnyView) -> any AnyView], type: Storage.Type) -> ViewStorage where Storage: AppStorage {
             print("Init button")
             let storage = ViewStorage(nil)
             Task {
@@ -67,7 +67,7 @@ public enum Backend1 {
             return storage
         }
 
-        public func update<Storage>(_ storage: ViewStorage, modifiers: [(any AnyView) -> any AnyView], updateProperties: Bool, type: Storage.Type) {
+        public func update<Storage>(_ storage: ViewStorage, modifiers: [@Sendable (any AnyView) -> any AnyView], updateProperties: Bool, type: Storage.Type) {
             Task {
                 if updateProperties {
                     print("Update button (label = \(label))")
@@ -98,7 +98,7 @@ public enum Backend1 {
             print("Update renderable")
         }
 
-        public func container<Storage>(modifiers: [(any AnyView) -> any AnyView], type: Storage.Type) -> ViewStorage where Storage: AppStorage {
+        public func container<Storage>(modifiers: [@Sendable (any AnyView) -> any AnyView], type: Storage.Type) -> ViewStorage where Storage: AppStorage {
             let storage = ViewStorage(nil)
             Task {
                 await storage.setRenderableContent(key: .mainContent, value: (content as [Renderable]).storages(type: MenuElement.self, fields: [:]))
@@ -106,7 +106,7 @@ public enum Backend1 {
             return storage
         }
 
-        public func update<Storage>(_ storage: ViewStorage, modifiers: [(any AnyView) -> any AnyView], updateProperties: Bool, type: Storage.Type) {
+        public func update<Storage>(_ storage: ViewStorage, modifiers: [@Sendable (any AnyView) -> any AnyView], updateProperties: Bool, type: Storage.Type) {
             Task {
                 (content as [Renderable]).update(await storage.getRenderableContent(key: .mainContent), updateProperties: updateProperties, type: MenuElement.self, fields: [:])
             }
@@ -158,7 +158,7 @@ public enum Backend1 {
             self.content = content()
         }
 
-        public func container<Storage>(modifiers: [(any Meta.AnyView) -> any Meta.AnyView], type: Storage.Type) -> Meta.ViewStorage where Storage : Meta.AppStorage {
+        public func container<Storage>(modifiers: [@Sendable (any Meta.AnyView) -> any Meta.AnyView], type: Storage.Type) -> Meta.ViewStorage where Storage : Meta.AppStorage {
             let storage = ViewStorage(nil)
             Task {
                 await storage.setContent(key: .mainContent, value: content.storages(modifiers: modifiers, type: type))
@@ -166,7 +166,7 @@ public enum Backend1 {
             return storage
         }
 
-        public func update<Storage>(_ storage: Meta.ViewStorage, modifiers: [(any Meta.AnyView) -> any Meta.AnyView], updateProperties: Bool, type: Storage.Type) where Storage : Meta.AppStorage {
+        public func update<Storage>(_ storage: Meta.ViewStorage, modifiers: [@Sendable (any Meta.AnyView) -> any Meta.AnyView], updateProperties: Bool, type: Storage.Type) where Storage : Meta.AppStorage {
             Task {
                 content.update(await storage.getContent(key: .mainContent), modifiers: modifiers, updateProperties: updateProperties, type: type)
             }
diff --git a/Tests/SampleBackends/Backend2.swift b/Tests/SampleBackends/Backend2.swift
index 98f4a3a..45c0491 100644
--- a/Tests/SampleBackends/Backend2.swift
+++ b/Tests/SampleBackends/Backend2.swift
@@ -54,7 +54,7 @@ public enum Backend2 {
             self.content = content()
         }
 
-        public func container<Storage>(modifiers: [(any Meta.AnyView) -> any Meta.AnyView], type: Storage.Type) -> Meta.ViewStorage where Storage : Meta.AppStorage {
+        public func container<Storage>(modifiers: [@Sendable (any Meta.AnyView) -> any Meta.AnyView], type: Storage.Type) -> Meta.ViewStorage where Storage : Meta.AppStorage {
             let storage = ViewStorage(nil)
             Task {
                 await storage.setContent(key: .mainContent, value: content.storages(modifiers: modifiers, type: type))
@@ -62,7 +62,7 @@ public enum Backend2 {
             return storage
         }
 
-        public func update<Storage>(_ storage: Meta.ViewStorage, modifiers: [(any Meta.AnyView) -> any Meta.AnyView], updateProperties: Bool, type: Storage.Type) where Storage : Meta.AppStorage {
+        public func update<Storage>(_ storage: Meta.ViewStorage, modifiers: [@Sendable (any Meta.AnyView) -> any Meta.AnyView], updateProperties: Bool, type: Storage.Type) where Storage : Meta.AppStorage {
             Task {
                 content.update(await storage.getContent(key: .mainContent), modifiers: modifiers, updateProperties: updateProperties, type: type)
             }