diff --git a/source/mijin/async/future.hpp b/source/mijin/async/future.hpp
index 5297ff7..ec59bbc 100644
--- a/source/mijin/async/future.hpp
+++ b/source/mijin/async/future.hpp
@@ -113,7 +113,7 @@ public: // modification
         isSet_ = true;
         sigSet.emit();
     }
-    constexpr void set() MIJIN_NOEXCEPT
+    constexpr void set() MIJIN_NOEXCEPT requires (std::is_same_v<TValue, void>)
     {
         MIJIN_ASSERT(!isSet_, "Trying to set a future twice!");
         isSet_ = true;