diff --git a/include/continuable/continuable-result.hpp b/include/continuable/continuable-result.hpp
index 7c62dc0..ff146b9 100644
--- a/include/continuable/continuable-result.hpp
+++ b/include/continuable/continuable-result.hpp
@@ -209,6 +209,11 @@ private:
   detail::container::flat_variant<surrogate_t, exception_t> variant_;
 };
 
+inline result<> make_result() {
+  result<> result;
+  result.set_value();
+  return result;
+}
 template <typename... T>
 auto make_result(T&&... values) {
   return result<detail::traits::unrefcv_t<T>...>(std::forward<T>(values)...);
diff --git a/include/continuable/detail/utility/flat-variant.hpp b/include/continuable/detail/utility/flat-variant.hpp
index 38a1ec4..54b09a3 100644
--- a/include/continuable/detail/utility/flat-variant.hpp
+++ b/include/continuable/detail/utility/flat-variant.hpp
@@ -361,7 +361,8 @@ private:
   detail::slot_t get_slot() const noexcept {
     // Check for invalid values especially for memory corruption,
     // the empty element is included.
-    assert(this->slot_ <= sizeof...(T));
+    assert((this->slot_ < sizeof...(T)) ||
+           (this->slot_ == detail::empty_slot::value));
     return this->slot_;
   }
   bool is_slot(detail::slot_t const slot) const noexcept {
diff --git a/include/continuable/detail/utility/result-trait.hpp b/include/continuable/detail/utility/result-trait.hpp
index 9d7012b..2101315 100644
--- a/include/continuable/detail/utility/result-trait.hpp
+++ b/include/continuable/detail/utility/result-trait.hpp
@@ -55,7 +55,10 @@ struct result_trait<> {
   }
 
   template <typename Result, typename Mapper>
-  static void visit(Result&& /*result*/, Mapper&& /*mapper*/) {
+  static auto visit(Result&& result, Mapper&& mapper) {
+    assert(result.is_value());
+    (void)result;
+    return util::invoke(std::forward<Mapper>(mapper));
   }
 };
 template <typename T>