diff --git a/chain.c b/chain.c
index 586fc95..3887053 100644
--- a/chain.c
+++ b/chain.c
@@ -51,7 +51,7 @@ int mm_chain_dp(int max_dist, int bw, int max_skip, int min_cnt, int min_sc, int
 			if (dd > bw) continue;
 			min_d = dq < dr? dq : dr;
 			sc = min_d > q_span? q_span : dq < dr? dq : dr;
-			sc -= dd? ilog2_32(dd) * 4 : 0;
+			sc -= dd? ilog2_32(dd) * 2 : 0;
 			if (min_d > q_span) sc -= ilog2_32(min_d) / 2;
 			sc += f[j];
 			if (sc > max_f) max_f = sc, max_j = j;
diff --git a/main.c b/main.c
index c27d6e9..9a504a2 100644
--- a/main.c
+++ b/main.c
@@ -10,7 +10,7 @@
 #include "minimap.h"
 #include "mmpriv.h"
 
-#define MM_VERSION "2.0-r170-pre"
+#define MM_VERSION "2.0-r171-pre"
 
 void liftrlimit()
 {