diff --git a/board/src/move.rs b/board/src/move.rs
index ade1ff8..08cf988 100644
--- a/board/src/move.rs
+++ b/board/src/move.rs
@@ -16,6 +16,7 @@ pub enum MakeMoveError {
     NoPiece,
     NoCapturedPiece,
     IllegalCastle,
+    IllegalSquare(Square),
 }
 
 mod castle {