diff --git a/encompass-cs/Engines/Spawner.cs b/encompass-cs/Engines/Spawner.cs
index a1f6e4e..5b42469 100644
--- a/encompass-cs/Engines/Spawner.cs
+++ b/encompass-cs/Engines/Spawner.cs
@@ -21,12 +21,12 @@ namespace Encompass
 
         public override void Update(double dt)
         {
-            foreach (var message in ReadMessages<TMessage>())
+            foreach (ref readonly var message in ReadMessages<TMessage>())
             {
                 Spawn(message);
             }
         }
 
-        protected abstract void Spawn(TMessage message);
+        protected abstract void Spawn(in TMessage message);
     }
 }
diff --git a/test/SpawnerTest.cs b/test/SpawnerTest.cs
index c0c5f0c..1c7c822 100644
--- a/test/SpawnerTest.cs
+++ b/test/SpawnerTest.cs
@@ -23,7 +23,7 @@ namespace Tests
         [Writes(typeof(TestComponent))]
         class TestSpawner : Spawner<SpawnMessageA>
         {
-            protected override void Spawn(SpawnMessageA message)
+            protected override void Spawn(in SpawnMessageA message)
             {
                 resultEntity = CreateEntity();
                 SetComponent(resultEntity, new TestComponent());