diff --git a/bam2bcf.h b/bam2bcf.h
index 54e5faaaa..972923d7c 100644
--- a/bam2bcf.h
+++ b/bam2bcf.h
@@ -1,7 +1,7 @@
 /*  bam2bcf.h -- variant calling.
 
     Copyright (C) 2010-2012 Broad Institute.
-    Copyright (C) 2012-2014 Genome Research Ltd.
+    Copyright (C) 2012-2014, 2019 Genome Research Ltd.
 
     Author: Heng Li <lh3@sanger.ac.uk>
 
@@ -99,7 +99,8 @@ typedef struct {
 } bcf_callret1_t;
 
 typedef struct {
-    int tid, pos;
+    int tid;
+    hts_pos_t pos;
     bcf_hdr_t *bcf_hdr;
     int a[5]; // alleles: ref, alt, alt2, alt3
     float qsum[5];  // for the QS tag
@@ -128,7 +129,7 @@ extern "C" {
     int bcf_call_combine(int n, const bcf_callret1_t *calls, bcf_callaux_t *bca, int ref_base /*4-bit*/, bcf_call_t *call);
     int bcf_call2bcf(bcf_call_t *bc, bcf1_t *b, bcf_callret1_t *bcr, int fmt_flag,
                      const bcf_callaux_t *bca, const char *ref);
-    int bcf_call_gap_prep(int n, int *n_plp, bam_pileup1_t **plp, int pos, bcf_callaux_t *bca, const char *ref,
+    int bcf_call_gap_prep(int n, int *n_plp, bam_pileup1_t **plp, hts_pos_t pos, bcf_callaux_t *bca, const char *ref,
                           const void *rghash);
     void bcf_callaux_clean(bcf_callaux_t *bca, bcf_call_t *call);
 
diff --git a/bam2bcf_indel.c b/bam2bcf_indel.c
index 9749d5bb7..104d10807 100644
--- a/bam2bcf_indel.c
+++ b/bam2bcf_indel.c
@@ -1,7 +1,7 @@
 /*  bam2bcf_indel.c -- indel caller.
 
     Copyright (C) 2010, 2011 Broad Institute.
-    Copyright (C) 2012-2014 Genome Research Ltd.
+    Copyright (C) 2012-2014, 2019 Genome Research Ltd.
 
     Author: Heng Li <lh3@sanger.ac.uk>
 
@@ -87,9 +87,10 @@ void bcf_call_del_rghash(void *_hash)
     kh_destroy(rg, hash);
 }
 
-static int tpos2qpos(const bam1_core_t *c, const uint32_t *cigar, int32_t tpos, int is_left, int32_t *_tpos)
+static int tpos2qpos(const bam1_core_t *c, const uint32_t *cigar, hts_pos_t tpos, hts_pos_t is_left, hts_pos_t *_tpos)
 {
-    int k, x = c->pos, y = 0, last_y = 0;
+    int k, y = 0, last_y = 0;
+    hts_pos_t x = c->pos;
     *_tpos = c->pos;
     for (k = 0; k < c->n_cigar; ++k) {
         int op = cigar[k] & BAM_CIGAR_MASK;
@@ -124,9 +125,10 @@ static inline int est_seqQ(const bcf_callaux_t *bca, int l, int l_run)
     return q < qh? q : qh;
 }
 
-static inline int est_indelreg(int pos, const char *ref, int l, char *ins4)
+static inline int est_indelreg(hts_pos_t pos, const char *ref, int l, char *ins4)
 {
-    int i, j, max = 0, max_i = pos, score = 0;
+    int j, max = 0, score = 0;
+    hts_pos_t i, max_i = pos;
     l = abs(l);
     for (i = pos + 1, j = 0; ref[i]; ++i, ++j) {
         if (ins4) score += (toupper(ref[i]) != "ACGTN"[(int)ins4[j%l]])? -10 : 1;
@@ -146,11 +148,12 @@ static inline int est_indelreg(int pos, const char *ref, int l, char *ins4)
             - 8: estimated sequence quality                     .. (aux>>8)&0xff
             - 8: indel quality                                  .. aux&0xff
  */
-int bcf_call_gap_prep(int n, int *n_plp, bam_pileup1_t **plp, int pos, bcf_callaux_t *bca, const char *ref,
+int bcf_call_gap_prep(int n, int *n_plp, bam_pileup1_t **plp, hts_pos_t pos, bcf_callaux_t *bca, const char *ref,
                       const void *rghash)
 {
-    int i, s, j, k, t, n_types, *types, max_rd_len, left, right, max_ins, *score1, *score2, max_ref2;
+    int s, k, t, n_types, *types, max_rd_len, max_ins, *score1, *score2, max_ref2;
     int N, K, l_run, ref_type, n_alt;
+    hts_pos_t i, j, left, right;
     char *inscns = 0, *ref2, *query, **ref_sample;
     khash_t(rg) *hash = (khash_t(rg)*)rghash;
     if (ref == 0 || bca == 0) return -1;
@@ -225,7 +228,7 @@ int bcf_call_gap_prep(int n, int *n_plp, bam_pileup1_t **plp, int pos, bcf_calla
             free(aux);
             // TODO revisit how/whether to control printing this warning
             if (hts_verbose >= 2)
-                fprintf(stderr, "[%s] excessive INDEL alleles at position %d. Skip the position.\n", __func__, pos + 1);
+                fprintf(stderr, "[%s] excessive INDEL alleles at position %"PRIhts_pos". Skip the position.\n", __func__, pos + 1);
             return -1;
         }
         types = (int*)calloc(n_types, sizeof(int));
@@ -274,7 +277,7 @@ int bcf_call_gap_prep(int n, int *n_plp, bam_pileup1_t **plp, int pos, bcf_calla
                 bam1_t *b = p->b;
                 uint32_t *cigar = bam_get_cigar(b);
                 uint8_t *seq = bam_get_seq(b);
-                int x = b->core.pos, y = 0;
+                hts_pos_t x = b->core.pos, y = 0;
                 for (k = 0; k < b->core.n_cigar; ++k) {
                     int op = cigar[k]&0xf;
                     int j, l = cigar[k]>>4;
@@ -382,7 +385,8 @@ int bcf_call_gap_prep(int n, int *n_plp, bam_pileup1_t **plp, int pos, bcf_calla
             // align each read to ref2
             for (i = 0; i < n_plp[s]; ++i, ++K) {
                 bam_pileup1_t *p = plp[s] + i;
-                int qbeg, qend, tbeg, tend, sc, kk;
+                int qbeg, qend, sc, kk;
+                hts_pos_t tbeg, tend;
                 uint8_t *seq = bam_get_seq(p->b);
                 uint32_t *cigar = bam_get_cigar(p->b);
                 if (p->b->core.flag&4) continue; // unmapped reads
diff --git a/bam_plcmd.c b/bam_plcmd.c
index 44d42a2bf..0497fb6f5 100644
--- a/bam_plcmd.c
+++ b/bam_plcmd.c
@@ -1,6 +1,6 @@
 /*  bam_plcmd.c -- mpileup subcommand.
 
-    Copyright (C) 2008-2015 Genome Research Ltd.
+    Copyright (C) 2008-2015, 2019 Genome Research Ltd.
     Portions copyright (C) 2009-2012 Broad Institute.
 
     Author: Heng Li <lh3@sanger.ac.uk>
@@ -64,9 +64,9 @@ static inline int printw(int c, FILE *fp)
     return 0;
 }
 
-static inline int pileup_seq(FILE *fp, const bam_pileup1_t *p, int pos,
-                             int ref_len, const char *ref, kstring_t *ks,
-                             int rev_del)
+static inline int pileup_seq(FILE *fp, const bam_pileup1_t *p, hts_pos_t pos,
+                              hts_pos_t ref_len, const char *ref, kstring_t *ks,
+                              int rev_del)
 {
     int j;
     if (p->is_head) {
@@ -162,7 +162,7 @@ typedef struct {
 typedef struct {
     char *ref[2];
     int ref_id[2];
-    int ref_len[2];
+    hts_pos_t ref_len[2];
 } mplp_ref_t;
 
 #define MPLP_REF_INIT {{NULL,NULL},{-1,-1},{0,0}}
@@ -228,7 +228,7 @@ static int build_auxlist(mplp_conf_t *conf, char *optstring) {
     return 0;
 }
 
-static int mplp_get_ref(mplp_aux_t *ma, int tid,  char **ref, int *ref_len) {
+static int mplp_get_ref(mplp_aux_t *ma, int tid, char **ref, hts_pos_t *ref_len) {
     mplp_ref_t *r = ma->ref;
 
     //printf("get ref %d {%d/%p, %d/%p}\n", tid, r->ref_id[0], r->ref[0], r->ref_id[1], r->ref[1]);
@@ -248,9 +248,10 @@ static int mplp_get_ref(mplp_aux_t *ma, int tid,  char **ref, int *ref_len) {
     }
     if (tid == r->ref_id[1]) {
         // Last, swap over
-        int tmp;
-        tmp = r->ref_id[0];  r->ref_id[0]  = r->ref_id[1];  r->ref_id[1]  = tmp;
-        tmp = r->ref_len[0]; r->ref_len[0] = r->ref_len[1]; r->ref_len[1] = tmp;
+        int tmp_id;
+        hts_pos_t tmp_len;
+        tmp_id  = r->ref_id[0];  r->ref_id[0]  = r->ref_id[1];  r->ref_id[1]  = tmp_id;
+        tmp_len = r->ref_len[0]; r->ref_len[0] = r->ref_len[1]; r->ref_len[1] = tmp_len;
 
         char *tc;
         tc = r->ref[0]; r->ref[0] = r->ref[1]; r->ref[1] = tc;
@@ -266,10 +267,10 @@ static int mplp_get_ref(mplp_aux_t *ma, int tid,  char **ref, int *ref_len) {
     r->ref_len[1] = r->ref_len[0];
 
     r->ref_id[0] = tid;
-    r->ref[0] = faidx_fetch_seq(ma->conf->fai,
+    r->ref[0] = faidx_fetch_seq64(ma->conf->fai,
                                 sam_hdr_tid2name(ma->h, r->ref_id[0]),
                                 0,
-                                INT_MAX,
+                                HTS_POS_MAX,
                                 &r->ref_len[0]);
 
     if (!r->ref[0]) {
@@ -287,10 +288,10 @@ static int mplp_get_ref(mplp_aux_t *ma, int tid,  char **ref, int *ref_len) {
 
 static void
 print_empty_pileup(FILE *fp, const mplp_conf_t *conf, const char *tname,
-                   int pos, int n, const char *ref, int ref_len)
+                   hts_pos_t pos, int n, const char *ref, hts_pos_t ref_len)
 {
     int i;
-    fprintf(fp, "%s\t%d\t%c", tname, pos+1, (ref && pos < ref_len)? ref[pos] : 'N');
+    fprintf(fp, "%s\t%"PRIhts_pos"\t%c", tname, pos+1, (ref && pos < ref_len)? ref[pos] : 'N');
     for (i = 0; i < n; ++i) {
         fputs("\t0\t*\t*", fp);
         if (conf->flag & MPLP_PRINT_QPOS)
@@ -314,7 +315,9 @@ static int mplp_func(void *data, bam1_t *b)
 {
     char *ref;
     mplp_aux_t *ma = (mplp_aux_t*)data;
-    int ret, skip = 0, ref_len;
+    int ret, skip = 0;
+    hts_pos_t ref_len;
+
     do {
         int has_ref;
         ret = ma->iter? sam_itr_next(ma->fp, ma->iter, b) : sam_read1(ma->fp, ma->h, b);
@@ -346,7 +349,7 @@ static int mplp_func(void *data, bam1_t *b)
         if (ma->conf->fai && b->core.tid >= 0) {
             has_ref = mplp_get_ref(ma, b->core.tid, &ref, &ref_len);
             if (has_ref && ref_len <= b->core.pos) { // exclude reads outside of the reference sequence
-                fprintf(stderr,"[%s] Skipping because %"PRId64" is outside of %d [ref:%d]\n",
+                fprintf(stderr,"[%s] Skipping because %"PRIhts_pos" is outside of %"PRIhts_pos" [ref:%d]\n",
                         __func__, (int64_t) b->core.pos, ref_len, b->core.tid);
                 skip = 1;
                 continue;
@@ -407,7 +410,8 @@ static int mpileup(mplp_conf_t *conf, int n, char **fn, char **fn_idx)
     extern void *bcf_call_add_rg(void *rghash, const char *hdtext, const char *list);
     extern void bcf_call_del_rghash(void *rghash);
     mplp_aux_t **data;
-    int i, tid, pos, *n_plp, beg0 = 0, end0 = INT_MAX, tid0 = 0, ref_len, max_depth, max_indel_depth;
+    int i, tid, *n_plp, tid0 = 0, max_depth, max_indel_depth;
+    hts_pos_t pos, beg0 = 0, end0 = HTS_POS_MAX, ref_len;
     const bam_pileup1_t **plp;
     mplp_ref_t mp_ref = MPLP_REF_INIT;
     bam_mplp_t iter;
@@ -667,10 +671,11 @@ static int mpileup(mplp_conf_t *conf, int n, char **fn, char **fn_idx)
     bam_mplp_set_maxcnt(iter, max_depth);
     bcf1_t *bcf_rec = bcf_init1();
     int ret;
-    int last_tid = -1, last_pos = -1;
+    int last_tid = -1;
+    hts_pos_t last_pos = -1;
 
     // begin pileup
-    while ( (ret=bam_mplp_auto(iter, &tid, &pos, n_plp, plp)) > 0) {
+    while ( (ret=bam_mplp64_auto(iter, &tid, &pos, n_plp, plp)) > 0) {
         if (conf->reg && (pos < beg0 || pos >= end0)) continue; // out of the region requested
         mplp_get_ref(data[0], tid, &ref, &ref_len);
         //printf("tid=%d len=%d ref=%p/%s\n", tid, ref_len, ref, ref);
@@ -739,7 +744,7 @@ static int mpileup(mplp_conf_t *conf, int n, char **fn, char **fn_idx)
             }
             if (conf->bed && tid >= 0 && !bed_overlap(conf->bed, sam_hdr_tid2name(h, tid), pos, pos+1)) continue;
 
-            fprintf(pileup_fp, "%s\t%d\t%c", sam_hdr_tid2name(h, tid), pos + 1, (ref && pos < ref_len)? ref[pos] : 'N');
+            fprintf(pileup_fp, "%s\t%"PRIhts_pos"\t%c", sam_hdr_tid2name(h, tid), pos + 1, (ref && pos < ref_len)? ref[pos] : 'N');
             for (i = 0; i < n; ++i) {
                 int j, cnt;
                 for (j = cnt = 0; j < n_plp[i]; ++j) {