--- include/frozen/bits/pmh.h	2024-09-01 12:04:54.942684661 +0100
+++ include/frozen/bits/pmh.h	2024-09-01 12:05:11.899749238 +0100
@@ -155,8 +155,8 @@
 
   constexpr pmh_tables(
       std::uint64_t first_seed,
-      carray<seed_or_index, M> first_table,
-      carray<std::size_t, M> second_table,
+      const carray<seed_or_index, M>& first_table,
+      const carray<std::size_t, M>& second_table,
       Hasher hash) noexcept
     : Hasher(hash)
     , first_seed_(first_seed)