diff --git a/source/mijin/async/coroutine.hpp b/source/mijin/async/coroutine.hpp
index 068b3a3..933fa02 100644
--- a/source/mijin/async/coroutine.hpp
+++ b/source/mijin/async/coroutine.hpp
@@ -49,10 +49,10 @@ class TaskLoop;
 template<typename TResult = void>
 class TaskBase;
 
-namespace impl
-{
 struct TaskCancelled : std::exception {};
 
+namespace impl
+{
 inline void throwIfCancelled();
 } // namespace impl
 
@@ -126,7 +126,7 @@ struct TaskAwaitableFuture
 
     [[nodiscard]] constexpr bool await_ready() const noexcept { return future->ready(); }
     constexpr void await_suspend(std::coroutine_handle<>) const noexcept {}
-    constexpr TValue await_resume() const noexcept
+    constexpr TValue await_resume() const
     {
         impl::throwIfCancelled();
         if constexpr (std::is_same_v<TValue, void>) {
@@ -606,7 +606,7 @@ inline TaskStatus TaskLoop::tickTask(StoredTask& task)
         {
             std::rethrow_exception(task.task->exception());
         }
-        catch(impl::TaskCancelled&) {} // ignore those
+        catch(TaskCancelled&) {} // ignore those
         catch(...)
         {
             if (uncaughtExceptionHandler_)