diff --git a/sud.c b/sud.c
index b5ff67e..4d84a22 100644
--- a/sud.c
+++ b/sud.c
@@ -18,7 +18,6 @@
 
 #include "sud.h"
 
-#include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -53,8 +52,6 @@ bool load(struct sudoku *sud, const char *ptr)
 enum update_res update(struct sudoku *sud, unsigned r, unsigned c, unsigned val)
 {
 	unsigned tr, tc;
-	assert(val < NDIGITS);
-
 	const uint16_t clearmask = ~(1 << val);
 
 	/* Update possible values of cells in same column. */