diff --git a/bwamem_pair.c b/bwamem_pair.c
index 51a844b..23c99ef 100644
--- a/bwamem_pair.c
+++ b/bwamem_pair.c
@@ -201,7 +201,7 @@ int mem_pair(const mem_opt_t *opt, int64_t l_pac, const uint8_t *pac, const mem_
 				if (dist > pes[dir].high) break;
 				if (dist < pes[dir].low)  continue;
 				ns = (dist - pes[dir].avg) / pes[dir].std;
-				q = (int)((v.a[i].y>>32) + (v.a[k].y>>32) + .721 * log(2. * erfc(fabs(ns) * M_SQRT1_2)) + .499); // .721 = 1/log(4)
+				q = (int)((v.a[i].y>>32) + (v.a[k].y>>32) + .721 * log(2. * erfc(fabs(ns) * M_SQRT1_2)) * opt->a + .499); // .721 = 1/log(4)
 				if (q < 0) q = 0;
 				p = kv_pushp(pair64_t, u);
 				p->y = (uint64_t)k<<32 | i;
diff --git a/main.c b/main.c
index c5b84be..905161f 100644
--- a/main.c
+++ b/main.c
@@ -3,7 +3,7 @@
 #include "utils.h"
 
 #ifndef PACKAGE_VERSION
-#define PACKAGE_VERSION "0.7.2-r363-beta"
+#define PACKAGE_VERSION "0.7.2-r364-beta"
 #endif
 
 int bwa_fa2pac(int argc, char *argv[]);