diff --git a/bwamem.c b/bwamem.c
index b9cdd82..5f51030 100644
--- a/bwamem.c
+++ b/bwamem.c
@@ -196,12 +196,12 @@ int mem_chain_weight(const mem_chain_t *c)
 		else if (s->qbeg + s->len > end) w += s->qbeg + s->len - end;
 		end = end > s->qbeg + s->len? end : s->qbeg + s->len;
 	}
-	tmp = w;
+	tmp = w; w = 0;
 	for (j = 0, end = 0; j < c->n; ++j) {
 		const mem_seed_t *s = &c->seeds[j];
 		if (s->rbeg >= end) w += s->len;
 		else if (s->rbeg + s->len > end) w += s->rbeg + s->len - end;
-		end = end > s->qbeg + s->len? end : s->qbeg + s->len;
+		end = end > s->rbeg + s->len? end : s->rbeg + s->len;
 	}
 	w = w < tmp? w : tmp;
 	return w < 1<<30? w : (1<<30)-1;
diff --git a/main.c b/main.c
index 5273c65..9727770 100644
--- a/main.c
+++ b/main.c
@@ -4,7 +4,7 @@
 #include "utils.h"
 
 #ifndef PACKAGE_VERSION
-#define PACKAGE_VERSION "0.7.8-r754-dirty"
+#define PACKAGE_VERSION "0.7.8-r758-dirty"
 #endif
 
 int bwa_fa2pac(int argc, char *argv[]);