diff --git a/bwaseqio.c b/bwaseqio.c
index 90abca0..e22d4cd 100644
--- a/bwaseqio.c
+++ b/bwaseqio.c
@@ -75,7 +75,7 @@ int bwa_trim_read(int trim_qual, bwa_seq_t *p)
 {
 	int s = 0, l, max = 0, max_l = p->len;
 	if (trim_qual < 1 || p->qual == 0) return 0;
-	for (l = p->len - 1; l >= BWA_MIN_RDLEN - 1; --l) {
+	for (l = p->len - 1; l >= BWA_MIN_RDLEN; --l) {
 		s += trim_qual - (p->qual[l] - 33);
 		if (s < 0) break;
 		if (s > max) max = s, max_l = l;