diff --git a/zecsy.hpp b/zecsy.hpp
index e879439..7626d6b 100644
--- a/zecsy.hpp
+++ b/zecsy.hpp
@@ -319,6 +319,11 @@ namespace zecsy
 
             archetypes[new_key].emplace_back(e);
 
+            if(archetypes[old_key].empty())
+            {
+                archetypes.erase(old_key);
+            }
+
             auto& pool = pools[id];
             auto index = pool.entity_to_index[e];
             pool.free_list.push_back(index);