diff --git a/bwtsw2_aux.c b/bwtsw2_aux.c
index 8f25734..5637b70 100644
--- a/bwtsw2_aux.c
+++ b/bwtsw2_aux.c
@@ -428,6 +428,7 @@ static void print_hits(const bntseq_t *bns, const bsw2opt_t *opt, bsw2seq1_t *ks
 				if (p->n_seeds < 2) c *= .2;
 				qual = (int)(c * (p->G - subo) * (250.0 / p->G + 0.03 / opt->a) + .499);
 				if (qual > 250) qual = 250;
+				if (qual < 0) qual = 0;
 				if (p->flag&1) qual = 0;
 			}
 			ksprintf(&str, "\t%d\t", qual);
diff --git a/bwtsw2_core.c b/bwtsw2_core.c
index f7b72de..cc3dc63 100644
--- a/bwtsw2_core.c
+++ b/bwtsw2_core.c
@@ -35,7 +35,7 @@ typedef struct {
 
 #include "ksort.h"
 KSORT_INIT_GENERIC(int)
-#define __hitG_lt(a, b) ((a).n_seeds > (b).n_seeds || ((a).n_seeds == (b).n_seeds && (a).G > (b).G))
+#define __hitG_lt(a, b) (((a).G + ((int)(a).n_seeds<<2)) > (b).G + ((int)(b).n_seeds<<2))
 KSORT_INIT(hitG, bsw2hit_t, __hitG_lt)
 
 static const bsw2cell_t g_default_cell = { 0, 0, MINUS_INF, MINUS_INF, MINUS_INF, 0, 0, 0, -1, -1, {-1, -1, -1, -1} };