namespace Stockfish {
-constexpr int PAWN_HISTORY_SIZE = 512;
+constexpr int PAWN_HISTORY_SIZE = 512; // has to be a power of 2
+
+static_assert((PAWN_HISTORY_SIZE & (PAWN_HISTORY_SIZE - 1)) == 0,
+ "PAWN_HISTORY_SIZE has to be a power of 2");
inline int pawn_structure(const Position& pos) { return pos.pawn_key() & (PAWN_HISTORY_SIZE - 1); }