diff --git a/cpp/async/handle_base.hpp b/cpp/async/handle_base.hpp
index 1e7776ad5f..d7d9eca5a6 100644
--- a/cpp/async/handle_base.hpp
+++ b/cpp/async/handle_base.hpp
@@ -237,6 +237,9 @@ class handle_base
     inline void set_value(T&& value)
     {
         std::unique_lock lock(data_->lock_);
+        if (is_cancelled(data_)) {
+            return;
+        }
         ASSERT(!has_result(data_));
         data_->result_ = Result(std::forward<T>(value));
         on_result_updated(std::move(lock), data_);
@@ -247,6 +250,9 @@ class handle_base
     inline void set_value(T&& value)
     {
         std::unique_lock lock(data_->lock_);
+        if (is_cancelled(data_)) {
+            return;
+        }
         ASSERT(!has_result(data_));
         data_->result_ = Result(std::forward<T>(value));
         on_result_updated(std::move(lock), data_);
@@ -257,6 +263,9 @@ class handle_base
     requires(std::is_void_v<Result>)
     {
         std::unique_lock lock(data_->lock_);
+        if (is_cancelled(data_)) {
+            return;
+        }
         ASSERT(!has_result(data_));
         data_->result_->set_fulfilled();
         on_result_updated(std::move(lock), data_);
@@ -265,6 +274,9 @@ class handle_base
     inline void set_exception(std::exception_ptr ex)
     {
         std::unique_lock lock(data_->lock_);
+        if (is_cancelled(data_)) {
+            return;
+        }
         ASSERT(!has_result(data_) || !data_->result_->succeeded());
         data_->result_ = std::move(ex);
         on_result_updated(std::move(lock), data_);
diff --git a/cpp/async/promise.hpp b/cpp/async/promise.hpp
index b7019733e2..2a5e42d89c 100644
--- a/cpp/async/promise.hpp
+++ b/cpp/async/promise.hpp
@@ -237,7 +237,8 @@ class promise
      * or re-raises the exception in case of failure.
      *
      * @pre The promise should have no callback registered. This is a mutually exclusive interface with set_callback.
-     * @warning The future will be forever locked if the promise will be cancelled.
+     * @warning Successful cancellation clears the callback and makes the future ready with
+     * std::future_errc::broken_promise, rather than delivering a result value.
      */
     [[nodiscard]] inline std::future<T> get_future()
     {