diff --git a/src/EcsWorld.cs b/src/EcsWorld.cs
index 4a7c860..8563944 100644
--- a/src/EcsWorld.cs
+++ b/src/EcsWorld.cs
@@ -389,7 +389,16 @@ namespace DCFApixels.DragonECS
             return *(entlong*)&x;
         }
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public unsafe EntitySlotInfo GetEntitySlotInfoDebug(int entityID)
+        public void InitEntitySlot(int entityID, short gen)
+        {
+#if (DEBUG && !DISABLE_DEBUG) || ENABLE_DRAGONECS_ASSERT_CHEKS
+            if (Count > 0) { Throw.World_MethodCalledAfterEntityCreation(nameof(InitEntitySlot)); }
+#endif
+            _entityDispenser.Upsize(entityID);
+            _entities[entityID].gen = gen;
+        }
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public EntitySlotInfo GetEntitySlotInfoDebug(int entityID)
         {
             return new EntitySlotInfo(entityID, _entities[entityID].gen, ID);
         }
diff --git a/src/Utils/Exceptions.cs b/src/Utils/Exceptions.cs
index a6655d2..19a4aa6 100644
--- a/src/Utils/Exceptions.cs
+++ b/src/Utils/Exceptions.cs
@@ -113,6 +113,11 @@ namespace DCFApixels.DragonECS.Internal
         {
             throw new EcsFrameworkException("This world can't be destroyed");
         }
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        public static void World_MethodCalledAfterEntityCreation(string methodName)
+        {
+            throw new EcsFrameworkException($"The method {methodName} can only be executed before creating entities in the world.");
+        }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
         internal static void Ent_ThrowIsNotAlive(entlong entity)