diff --git a/src/World.cs b/src/World.cs
index 0dcc689..f139353 100644
--- a/src/World.cs
+++ b/src/World.cs
@@ -105,6 +105,8 @@ namespace MoonTools.ECS
 				{
 					TypeToFilter[typeId].Add(filter);
 				}
+
+				FilterIndex.Add(signature, filter);
 			}
 
 			return filter;