diff --git a/lib/libc/printf.c b/lib/libc/printf.c
index 4480e94..d50876d 100644
--- a/lib/libc/printf.c
+++ b/lib/libc/printf.c
@@ -166,6 +166,7 @@
 					padn = (padn * 10) + (ch - '0');
 					fmt++;
 				}
+				assert(0); /* Unreachable */
 			default:
 				/* Exit on any other format specifier */
 				return -1;