diff --git a/crates/eframe/src/native/epi_integration.rs b/crates/eframe/src/native/epi_integration.rs
index ab1d09ff2..62da69765 100644
--- a/crates/eframe/src/native/epi_integration.rs
+++ b/crates/eframe/src/native/epi_integration.rs
@@ -483,7 +483,7 @@ impl EpiIntegration {
         app: &mut dyn epi::App,
         window: &winit::window::Window,
         egui_winit: &mut egui_winit::State,
-        viewport_ui_cb: &Option<Arc<Box<ViewportUiCallback>>>,
+        viewport_ui_cb: &Option<Arc<ViewportUiCallback>>,
         id_pair: ViewportIdPair,
     ) -> egui::FullOutput {
         let frame_start = std::time::Instant::now();
diff --git a/crates/eframe/src/native/run.rs b/crates/eframe/src/native/run.rs
index a9c7895c0..203d89f71 100644
--- a/crates/eframe/src/native/run.rs
+++ b/crates/eframe/src/native/run.rs
@@ -503,7 +503,7 @@ mod glow_integration {
         id_pair: ViewportIdPair,
 
         /// The user-callback that shows the ui.
-        viewport_ui_cb: Option<Arc<Box<ViewportUiCallback>>>,
+        viewport_ui_cb: Option<Arc<ViewportUiCallback>>,
 
         egui_winit: Option<egui_winit::State>,
     }
@@ -1854,7 +1854,7 @@ mod wgpu_integration {
         egui_winit: Rc<RefCell<Option<egui_winit::State>>>,
 
         /// `None` for sync viewports.
-        viewport_ui_cb: Option<Arc<Box<ViewportUiCallback>>>,
+        viewport_ui_cb: Option<Arc<ViewportUiCallback>>,
 
         parent_id: ViewportId,
     }
diff --git a/crates/egui/src/viewport.rs b/crates/egui/src/viewport.rs
index c073d9405..1af8e9b1b 100644
--- a/crates/egui/src/viewport.rs
+++ b/crates/egui/src/viewport.rs
@@ -662,7 +662,7 @@ pub(crate) struct ViewportState {
     /// The user-code that shows the GUI, used for deferred viewports.
     ///
     /// `None` for immediate viewports.
-    pub(crate) viewport_ui_cb: Option<Arc<Box<ViewportUiCallback>>>,
+    pub(crate) viewport_ui_cb: Option<Arc<ViewportUiCallback>>,
 }
 
 /// Describes a viewport, i.e. a native window.
@@ -676,5 +676,5 @@ pub struct ViewportOutput {
     /// The user-code that shows the GUI, used for deferred viewports.
     ///
     /// `None` for immediate viewports and the ROOT viewport.
-    pub viewport_ui_cb: Option<Arc<Box<ViewportUiCallback>>>,
+    pub viewport_ui_cb: Option<Arc<ViewportUiCallback>>,
 }