Index: uspace/app/tetris/tetris.c
===================================================================
--- uspace/app/tetris/tetris.c	(revision 79ae36ddc409577eb0da3750b3a7280e034566a2)
+++ uspace/app/tetris/tetris.c	(revision b0f00a9ed1b00bda8a286a4c4bbe625a7f410bc6)
@@ -291,5 +291,5 @@
 		for (j = i + 1; j <= 5; j++) {
 			if (keys[i] == keys[j])
-				errx(1, "duplicate command keys specified.");
+				errx(1, "%s", "duplicate command keys specified.");
 		}