--- a/command.c	Tue May 15 23:32:50 2007 +0000
+++ b/command.c	Wed May 16 08:21:16 2007 +0000
@@ -335,7 +335,7 @@
 	CommandProc *proc;
 
 	/* Do not even think about executing out-of-bounds tile-commands */
-	if (tile >= MapSize()) {
+	if (tile >= MapSize() || IsTileType(tile, MP_VOID)) {
 		_cmd_text = NULL;
 		return CMD_ERROR;
 	}
@@ -413,7 +413,7 @@
 	int y = TileY(tile) * TILE_SIZE;
 
 	/* Do not even think about executing out-of-bounds tile-commands */
-	if (tile >= MapSize()) {
+	if (tile >= MapSize() || IsTileType(tile, MP_VOID)) {
 		_cmd_text = NULL;
 		return false;
 	}