diff --git a/src/types.h b/src/types.h
index 519f6af8..a95420ca 100644
--- a/src/types.h
+++ b/src/types.h
@@ -209,7 +209,7 @@ const Piece Pieces[] = { W_PAWN, W_KNIGHT, W_BISHOP, W_ROOK, W_QUEEN, W_KING,
                          B_PAWN, B_KNIGHT, B_BISHOP, B_ROOK, B_QUEEN, B_KING };
 extern Value PieceValue[PHASE_NB][PIECE_NB];
 
-enum Depth {
+enum Depth : int {
 
   ONE_PLY = 1,