--- a/src/game.c
+++ b/src/game.c
@@ -642,7 +642,7 @@
 		  (game, prev_winner, c, ((i + prev_winner) % 4),
 		   game->players[((i + prev_winner) % 4)]->turn, &err))
 		{
-		  g_message (err->message);
+		  g_message ("%s", err->message);
 		  turn_nok = TRUE;
 		  game->players[((i + prev_winner) % 4)]->ready =
 		    MT_PLAYER_READY_SEND_NOK_FOR_CARD;