Index: uspace/app/tetris/tetris.c
===================================================================
--- uspace/app/tetris/tetris.c	(revision 1e891d04a007a50f5ff2f8d3cda19631f92b76e6)
+++ uspace/app/tetris/tetris.c	(revision ceb07b910b5e73c39a65b12cf582bb6446532ffe)
@@ -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.");
 		}