diff --git a/bntseq.c b/bntseq.c
index 65f7e93..ed4ce6a 100644
--- a/bntseq.c
+++ b/bntseq.c
@@ -69,7 +69,7 @@ void bns_dump(const bntseq_t *bns, const char *prefix)
 	FILE *fp;
 	int i;
 	{ // dump .ann
-		strcpy(str, prefix); strcat(str, ".ann");
+		snprintf(str, sizeof(str), "%s.ann", prefix);
 		fp = xopen(str, "w");
 		err_fprintf(fp, "%lld %d %u\n", (long long)bns->l_pac, bns->n_seqs, bns->seed);
 		for (i = 0; i != bns->n_seqs; ++i) {
@@ -83,7 +83,7 @@ void bns_dump(const bntseq_t *bns, const char *prefix)
 		err_fclose(fp);
 	}
 	{ // dump .amb
-		strcpy(str, prefix); strcat(str, ".amb");
+		snprintf(str, sizeof(str), "%s.amb", prefix);
 		fp = xopen(str, "w");
 		err_fprintf(fp, "%lld %d %u\n", (long long)bns->l_pac, bns->n_seqs, bns->n_holes);
 		for (i = 0; i != bns->n_holes; ++i) {
@@ -171,12 +171,13 @@ bntseq_t *bns_restore(const char *prefix)
 	char ann_filename[1024], amb_filename[1024], pac_filename[1024], alt_filename[1024];
 	FILE *fp;
 	bntseq_t *bns;
-	strcat(strcpy(ann_filename, prefix), ".ann");
-	strcat(strcpy(amb_filename, prefix), ".amb");
-	strcat(strcpy(pac_filename, prefix), ".pac");
+	snprintf(ann_filename, sizeof(ann_filename), "%s.ann", prefix);
+	snprintf(amb_filename, sizeof(amb_filename), "%s.amb", prefix);
+	snprintf(pac_filename, sizeof(pac_filename), "%s.pac", prefix);
 	bns = bns_restore_core(ann_filename, amb_filename, pac_filename);
 	if (bns == 0) return 0;
-	if ((fp = fopen(strcat(strcpy(alt_filename, prefix), ".alt"), "r")) != 0) { // read .alt file if present
+	snprintf(alt_filename, sizeof(alt_filename), "%s.alt", prefix);
+	if ((fp = fopen(alt_filename, "r")) != 0) { // read .alt file if present
 		char str[1024];
 		khash_t(str) *h;
 		int c, i, absent;
@@ -197,7 +198,13 @@ bntseq_t *bns_restore(const char *prefix)
 				}
 				while (c != '\n' && c != EOF) c = fgetc(fp);
 				i = 0;
-			} else str[i++] = c; // FIXME: potential segfault here
+			} else {
+				if (i >= 1022) {
+					fprintf(stderr, "[E::%s] sequence name longer than 1023 characters. Abort!\n", __func__);
+					exit(1);
+				}
+				str[i++] = c;
+			}
 		}
 		kh_destroy(str, h);
 		fclose(fp);
@@ -294,7 +301,7 @@ int64_t bns_fasta2bntseq(gzFile fp_fa, const char *prefix, int for_only)
 	bns->ambs = (bntamb1_t*)calloc(m_holes, sizeof(bntamb1_t));
 	pac = calloc(m_pac/4, 1);
 	q = bns->ambs;
-	strcpy(name, prefix); strcat(name, ".pac");
+	snprintf(name, sizeof(name), "%s.pac", prefix);
 	fp = xopen(name, "wb");
 	// read sequences
 	while (kseq_read(seq) >= 0) pac = add1(seq, bns, pac, &m_pac, &m_seqs, &m_holes, &q);