diff --git a/sud.c b/sud.c
index 364a9ba..172dfe6 100644
--- a/sud.c
+++ b/sud.c
@@ -116,12 +116,6 @@ enum update_res update(struct sudoku *sud, unsigned r, unsigned c, unsigned val)
 	unsigned tr, tc;
 	assert(val < NDIGITS);
 
-	/* Check that the cell is undetermined and the value is allowed. */
-	if (sud->cells[r][c].det)
-		return ALREADY_DET;
-	if (!sud->cells[r][c].pvals[val])
-		return NOT_ALLOWED;
-
 	/* Update possible values of cells in same column. */
 	for (tr = 0; tr < NDIGITS; ++tr) {
 		if (tr == r || sud->cells[tr][c].det)