// Proceed according to the type of the moving piece.
if (type_of_piece(pc) == PAWN)
{
+ // Move direction must be compatible with pawn color
+ int direction = to - from;
+ if ((us == WHITE) != (direction > 0))
+ return false;
+
// If the destination square is on the 8/1th rank, the move must
// be a promotion.
if ( ( (square_rank(to) == RANK_8 && us == WHITE)
// Proceed according to the square delta between the source and
// destionation squares.
- switch (to - from)
+ switch (direction)
{
case DELTA_NW:
case DELTA_NE: