diff --git a/include/Continuable.h b/include/Continuable.h
index 6874a92..f3cafbf 100644
--- a/include/Continuable.h
+++ b/include/Continuable.h
@@ -555,12 +555,13 @@ namespace detail
             // TODO Improve the lock here
             std::lock_guard<std::mutex> guard(lock);
             {
-                std::cout << "storing..." << std::endl;
+                // Never call callbacks twice!
+                assert(partitions_left);
 
                 // If all partitions have completed invoke the final callback.
                 if (--partitions_left == 0)
                 {
-                    fu::invoke_from_tuple(callback, result);
+                    fu::invoke_from_tuple(std::move(callback), std::move(result));
                 }
             }
         }
diff --git a/test.cpp b/test.cpp
index ae8b9f9..20f0b8a 100644
--- a/test.cpp
+++ b/test.cpp
@@ -413,15 +413,15 @@ int main(int /*argc*/, char** /*argv*/)
                 return CastSpellPromise(20);
             },
             [] {
-                return make_continuable([](Callback<bool, bool, double, std::string>&& callback)
+                return make_continuable([](Callback<bool, bool, double, std::unique_ptr<std::string>>&& callback)
                 {
-                    callback(true, false, 0.3f, std::string("oh, all work is done!"));
+                    callback(true, false, 0.3f, std::make_unique<std::string>("oh, all work is done!"));
                 });
             },
             TrivialPromise())
-        .then([](SpellCastResult r0, SpellCastResult r1, bool r2, bool r3, double r4, std::string message)
+        .then([](SpellCastResult r0, SpellCastResult r1, bool r2, bool r3, double r4, std::unique_ptr<std::string> message)
         {
-            return TrivialPromise("Lets see... ").then(Log(message));
+            return TrivialPromise("Lets see... ").then(Log(*message));
         })
         .then([]
         {