diff --git a/board/src/builder.rs b/board/src/builder.rs
index b20cd41..e4f8ec0 100644
--- a/board/src/builder.rs
+++ b/board/src/builder.rs
@@ -89,18 +89,18 @@ impl Builder {
     }
 
     pub fn build(&self) -> Board {
-        let pieces = self
+        let pieces: PieceSet = self
             .pieces
             .iter()
-            .map(PlacedPiece::from)
             .filter(Self::is_piece_placement_valid)
-            .collect::<PieceBitBoards>();
+            .collect();
 
         let mut flags = self.flags;
 
         for color in Color::ALL {
             for castle in Castle::ALL {
                 let parameters = castle.parameters(color);
+
                 let has_rook_on_starting_square = self
                     .pieces
                     .get(parameters.rook_origin_square())