diff --git a/js/chess.js b/js/chess.js
index 23e0a2a..860433a 100644
--- a/js/chess.js
+++ b/js/chess.js
@@ -161,18 +161,24 @@ function legalMoves(board, side, type, from, canCapture){
          scanPath(legals, board, side, from, false, dir[0], dir[1], 0);
       }
       if (from[0] === 'e' && from[1] === (isDark(side) ? '8' : '1')) {
+         const other = otherSide(side);
          /* check for castling conditions */
          if (!hasMoved(board, side, from)) {
             if (boardGet(board, 'f' + from[1], side) === ' ' &&
+                boardGet(board, 'f' + from[1], other) === ' ' &&
                 boardGet(board, 'g' + from[1], side) === ' ' &&
+                boardGet(board, 'g' + from[1], other) === ' ' &&
                 boardGet(board, 'h' + from[1], side) === 'r') {
                if (!hasMoved(board, side, 'h' + from[1])) {
                   legals.push('g' + from[1]);
                }
             }
             if (boardGet(board, 'd' + from[1], side) === ' ' &&
+                boardGet(board, 'd' + from[1], other) === ' ' &&
                 boardGet(board, 'c' + from[1], side) === ' ' &&
+                boardGet(board, 'c' + from[1], other) === ' ' &&
                 boardGet(board, 'b' + from[1], side) === ' ' &&
+                boardGet(board, 'b' + from[1], other) === ' ' &&
                 boardGet(board, 'a' + from[1], side) === 'r') {
                if (!hasMoved(board, side, 'a' + from[1])) {
                   legals.push('c' + from[1]);