diff --git a/chain.c b/chain.c
index 95abf5e..a2f7ac5 100644
--- a/chain.c
+++ b/chain.c
@@ -19,7 +19,7 @@ static inline int ilog2_32(uint32_t v)
 	return (t = v>>8) ? 8 + LogTable256[t] : LogTable256[v];
 }
 
-mm128_t *mm_chain_dp(int max_dist_x, int max_dist_y, int bw, int max_skip, int max_iter, int min_cnt, int min_sc, int is_cdna, int n_segs, int64_t n, mm128_t *a, int *n_u_, uint64_t **_u, void *km)
+mm128_t *mm_chain_dp(int max_dist_x, int max_dist_y, int bw, int max_skip, int max_iter, int min_cnt, int min_sc, float gap_scale, int is_cdna, int n_segs, int64_t n, mm128_t *a, int *n_u_, uint64_t **_u, void *km)
 { // TODO: make sure this works when n has more than 32 bits
 	int32_t k, *f, *p, *t, *v, n_u, n_v;
 	int64_t i, j, st = 0;
@@ -52,7 +52,7 @@ mm128_t *mm_chain_dp(int max_dist_x, int max_dist_y, int bw, int max_skip, int m
 		if (i - st > max_iter) st = i - max_iter;
 		for (j = i - 1; j >= st; --j) {
 			int64_t dr = ri - a[j].x;
-			int32_t dq = qi - (int32_t)a[j].y, dd, sc, log_dd;
+			int32_t dq = qi - (int32_t)a[j].y, dd, sc, log_dd, gap_cost;
 			int32_t sidj = (a[j].y & MM_SEED_SEG_MASK) >> MM_SEED_SEG_SHIFT;
 			if ((sidi == sidj && dr == 0) || dq <= 0) continue; // don't skip if an anchor is used by multiple segments; see below
 			if ((sidi == sidj && dq > max_dist_y) || dq > max_dist_x) continue;
@@ -62,14 +62,16 @@ mm128_t *mm_chain_dp(int max_dist_x, int max_dist_y, int bw, int max_skip, int m
 			min_d = dq < dr? dq : dr;
 			sc = min_d > q_span? q_span : dq < dr? dq : dr;
 			log_dd = dd? ilog2_32(dd) : 0;
+			gap_cost = 0;
 			if (is_cdna || sidi != sidj) {
 				int c_log, c_lin;
 				c_lin = (int)(dd * .01 * avg_qspan);
 				c_log = log_dd;
 				if (sidi != sidj && dr == 0) ++sc; // possibly due to overlapping paired ends; give a minor bonus
-				else if (dr > dq || sidi != sidj) sc -= c_lin < c_log? c_lin : c_log;
-				else sc -= c_lin + (c_log>>1);
-			} else sc -= (int)(dd * .01 * avg_qspan) + (log_dd>>1);
+				else if (dr > dq || sidi != sidj) gap_cost = c_lin < c_log? c_lin : c_log;
+				else gap_cost = c_lin + (c_log>>1);
+			} else gap_cost = (int)(dd * .01 * avg_qspan) + (log_dd>>1);
+			sc -= (int)((double)gap_cost * gap_scale + .499);
 			sc += f[j];
 			if (sc > max_f) {
 				max_f = sc, max_j = j;
diff --git a/main.c b/main.c
index 63730c1..d6535e7 100644
--- a/main.c
+++ b/main.c
@@ -7,7 +7,7 @@
 #include "mmpriv.h"
 #include "ketopt.h"
 
-#define MM_VERSION "2.17-r963-dirty"
+#define MM_VERSION "2.17-r965-dirty"
 
 #ifdef __linux__
 #include <sys/resource.h>
@@ -67,6 +67,7 @@ static ko_longopt_t long_options[] = {
 	{ "junc-bed",       ko_required_argument, 340 },
 	{ "junc-bonus",     ko_required_argument, 341 },
 	{ "sam-hit-only",   ko_no_argument,       342 },
+	{ "chain-gap-scale",ko_required_argument, 343 },
 	{ "help",           ko_no_argument,       'h' },
 	{ "max-intron-len", ko_required_argument, 'G' },
 	{ "version",        ko_no_argument,       'V' },
@@ -211,6 +212,7 @@ int main(int argc, char *argv[])
 		else if (c == 340) junc_bed = o.arg; // --junc-bed
 		else if (c == 341) opt.junc_bonus = atoi(o.arg); // --junc-bonus
 		else if (c == 342) opt.flag |= MM_F_SAM_HIT_ONLY; // --sam-hit-only
+		else if (c == 343) opt.chain_gap_scale = atof(o.arg); // --chain-gap-scale
 		else if (c == 314) { // --frag
 			yes_or_no(&opt, MM_F_FRAG_MODE, o.longidx, o.arg, 1);
 		} else if (c == 315) { // --secondary
diff --git a/map.c b/map.c
index 58e74fc..8cfd8f4 100644
--- a/map.c
+++ b/map.c
@@ -313,7 +313,7 @@ void mm_map_frag(const mm_idx_t *mi, int n_segs, const int *qlens, const char **
 		if (max_chain_gap_ref < opt->max_gap) max_chain_gap_ref = opt->max_gap;
 	} else max_chain_gap_ref = opt->max_gap;
 
-	a = mm_chain_dp(max_chain_gap_ref, max_chain_gap_qry, opt->bw, opt->max_chain_skip, opt->max_chain_iter, opt->min_cnt, opt->min_chain_score, is_splice, n_segs, n_a, a, &n_regs0, &u, b->km);
+	a = mm_chain_dp(max_chain_gap_ref, max_chain_gap_qry, opt->bw, opt->max_chain_skip, opt->max_chain_iter, opt->min_cnt, opt->min_chain_score, opt->chain_gap_scale, is_splice, n_segs, n_a, a, &n_regs0, &u, b->km);
 
 	if (opt->max_occ > opt->mid_occ && rep_len > 0) {
 		int rechain = 0;
@@ -335,7 +335,7 @@ void mm_map_frag(const mm_idx_t *mi, int n_segs, const int *qlens, const char **
 			kfree(b->km, mini_pos);
 			if (opt->flag & MM_F_HEAP_SORT) a = collect_seed_hits_heap(b->km, opt, opt->max_occ, mi, qname, &mv, qlen_sum, &n_a, &rep_len, &n_mini_pos, &mini_pos);
 			else a = collect_seed_hits(b->km, opt, opt->max_occ, mi, qname, &mv, qlen_sum, &n_a, &rep_len, &n_mini_pos, &mini_pos);
-			a = mm_chain_dp(max_chain_gap_ref, max_chain_gap_qry, opt->bw, opt->max_chain_skip, opt->max_chain_iter, opt->min_cnt, opt->min_chain_score, is_splice, n_segs, n_a, a, &n_regs0, &u, b->km);
+			a = mm_chain_dp(max_chain_gap_ref, max_chain_gap_qry, opt->bw, opt->max_chain_skip, opt->max_chain_iter, opt->min_cnt, opt->min_chain_score, opt->chain_gap_scale, is_splice, n_segs, n_a, a, &n_regs0, &u, b->km);
 		}
 	}
 	b->frag_gap = max_chain_gap_ref;
diff --git a/minimap.h b/minimap.h
index cdf955f..8837fdb 100644
--- a/minimap.h
+++ b/minimap.h
@@ -117,6 +117,7 @@ typedef struct {
 	int max_chain_skip, max_chain_iter;
 	int min_cnt;         // min number of minimizers on each chain
 	int min_chain_score; // min chaining score
+	float chain_gap_scale;
 
 	float mask_level;
 	float pri_ratio;
diff --git a/minimap2.1 b/minimap2.1
index ff0b922..faa42f3 100644
--- a/minimap2.1
+++ b/minimap2.1
@@ -245,6 +245,9 @@ Check up to
 partial chains during chaining [5000]. This is a heuristic to avoid quadratic
 time complexity in the worst case.
 .TP
+.BI --chain-gap-scale \ FLOAT
+Scale of gap cost during chaining [1.0]
+.TP
 .B --no-long-join
 Disable the long gap patching heuristic. When this option is applied, the
 maximum alignment gap is mostly controlled by
diff --git a/mmpriv.h b/mmpriv.h
index c1164e2..e42f0df 100644
--- a/mmpriv.h
+++ b/mmpriv.h
@@ -69,7 +69,7 @@ void mm_write_sam3(kstring_t *s, const mm_idx_t *mi, const mm_bseq1_t *t, int se
 void mm_idxopt_init(mm_idxopt_t *opt);
 const uint64_t *mm_idx_get(const mm_idx_t *mi, uint64_t minier, int *n);
 int32_t mm_idx_cal_max_occ(const mm_idx_t *mi, float f);
-mm128_t *mm_chain_dp(int max_dist_x, int max_dist_y, int bw, int max_skip, int max_iter, int min_cnt, int min_sc, int is_cdna, int n_segs, int64_t n, mm128_t *a, int *n_u_, uint64_t **_u, void *km);
+mm128_t *mm_chain_dp(int max_dist_x, int max_dist_y, int bw, int max_skip, int max_iter, int min_cnt, int min_sc, float gap_scale, int is_cdna, int n_segs, int64_t n, mm128_t *a, int *n_u_, uint64_t **_u, void *km);
 mm_reg1_t *mm_align_skeleton(void *km, const mm_mapopt_t *opt, const mm_idx_t *mi, int qlen, const char *qstr, int *n_regs_, mm_reg1_t *regs, mm128_t *a);
 
 mm_reg1_t *mm_gen_regs(void *km, uint32_t hash, int qlen, int n_u, uint64_t *u, mm128_t *a);
diff --git a/options.c b/options.c
index 2e6a43a..171e9bc 100644
--- a/options.c
+++ b/options.c
@@ -24,6 +24,7 @@ void mm_mapopt_init(mm_mapopt_t *opt)
 	opt->max_gap_ref = -1;
 	opt->max_chain_skip = 25;
 	opt->max_chain_iter = 5000;
+	opt->chain_gap_scale = 1.0f;
 
 	opt->mask_level = 0.5f;
 	opt->pri_ratio = 0.8f;
diff --git a/python/cmappy.pxd b/python/cmappy.pxd
index 7545cb8..8564ac0 100644
--- a/python/cmappy.pxd
+++ b/python/cmappy.pxd
@@ -20,6 +20,7 @@ cdef extern from "minimap.h":
 		int max_chain_skip, max_chain_iter
 		int min_cnt
 		int min_chain_score
+		float chain_gap_scale
 		float mask_level
 		float pri_ratio
 		int best_n