diff --git a/board/src/builder.rs b/board/src/builder.rs
index e4f8ec0..f7f7cdf 100644
--- a/board/src/builder.rs
+++ b/board/src/builder.rs
@@ -8,7 +8,7 @@ pub struct Builder {
     player_to_move: Color,
     flags: Flags,
     pieces: Mailbox,
-    kings: [Option<Square>; 2],
+    kings: [Option<Square>; Color::NUM],
     en_passant: Option<EnPassant>,
     ply_counter: u16,
     move_number: u16,