diff --git a/support-lib/cpp/Future.hpp b/support-lib/cpp/Future.hpp
index fe732ad8..f04adaa3 100644
--- a/support-lib/cpp/Future.hpp
+++ b/support-lib/cpp/Future.hpp
@@ -383,16 +383,17 @@ class Future {
             this->_promise.setValue(std::forward<V>(value));
         }
     };
-    template <>
-    struct PromiseType<void>: PromiseTypeBase {
-        void return_void() {
-            this->_promise.setValue();
-        }
-    };
     using promise_type = PromiseType<T>;
-#endif
 };
 
+template<> template<> struct Future<void>::PromiseType<void>:PromiseTypeBase {
+    void return_void() {
+        this->_promise.setValue();
+    }
+}
+
+#endif
+
 template <typename T>
 Future<T> detail::PromiseBase<T>::getFuture() {
     return Future<T>(_sharedStateReadOnly);