diff --git a/src/repr/bitboard.rs b/src/repr/bitboard.rs
index 865116a..a09060c 100644
--- a/src/repr/bitboard.rs
+++ b/src/repr/bitboard.rs
@@ -12,7 +12,7 @@ pub type BitBoardInner = u64;
 pub struct BitBoard(BitBoardInner);
 
 // BitBoard should be big enough to fit all points on the board
-const_assert!(std::mem::size_of::<BitBoard>() * 8 >= Board::AREA.0 as usize);
+const_assert!(BitBoardInner::BITS >= Board::AREA.0 as u32);
 
 impl BitBoard {
     #[allow(clippy::new_without_default)]