diff --git a/src/bitboard.rs b/src/bitboard.rs
index dd225fa..3669299 100644
--- a/src/bitboard.rs
+++ b/src/bitboard.rs
@@ -4,6 +4,7 @@ use crate::board::*;
 
 /// A set of squares.
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
+#[repr(transparent)]
 pub struct Bitboard(pub u64);
 
 impl Bitboard {
diff --git a/src/position.rs b/src/position.rs
index 11eaba0..387a82b 100644
--- a/src/position.rs
+++ b/src/position.rs
@@ -57,6 +57,7 @@ use core::ops::ControlFlow;
 /// considered stable.
 #[must_use]
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord)]
+#[repr(transparent)]
 pub struct Position(Setup);
 
 const PAWN: u8 = Role::Pawn as u8;