diff --git a/CHANGELOG.md b/CHANGELOG.md
index f53bb569..c8be853d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 # Unreleased
 
+- On macOS, fix crash when starting maximized without decorations.
 - On macOS, fix application not to terminate on `run_return`.
 - On Wayland, fix cursor icon updates on window borders when using CSD.
 - On Wayland, under mutter(GNOME Wayland), fix CSD being behind the status bar, when starting window in maximized mode.
diff --git a/src/platform_impl/macos/util/async.rs b/src/platform_impl/macos/util/async.rs
index ad1a891b..c2d117b6 100644
--- a/src/platform_impl/macos/util/async.rs
+++ b/src/platform_impl/macos/util/async.rs
@@ -60,11 +60,15 @@ pub unsafe fn set_style_mask_async(ns_window: id, ns_view: id, mask: NSWindowSty
 }
 pub unsafe fn set_style_mask_sync(ns_window: id, ns_view: id, mask: NSWindowStyleMask) {
     let context = SetStyleMaskData::new_ptr(ns_window, ns_view, mask);
-    dispatch_sync_f(
-        dispatch_get_main_queue(),
-        context as *mut _,
-        set_style_mask_callback,
-    );
+    if msg_send![class!(NSThread), isMainThread] {
+        set_style_mask_callback(context as *mut _);
+    } else {
+        dispatch_sync_f(
+            dispatch_get_main_queue(),
+            context as *mut _,
+            set_style_mask_callback,
+        );
+    }
 }
 
 struct SetContentSizeData {