diff --git a/LICENSE.TXT b/LICENSE.TXT
index 1ebca50..b1aebb5 100644
--- a/LICENSE.TXT
+++ b/LICENSE.TXT
@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2017 IP2Location.com
+Copyright (c) 2019 IP2Location.com
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/README.md b/README.md
index cd7d4c7..fb76cb7 100644
--- a/README.md
+++ b/README.md
@@ -87,4 +87,4 @@ Use the IPv6 BIN file if you need to query BOTH IPv4 and IPv6 addresses.
 Copyright
 =========
 
-Copyright (C) 2018 by IP2Location.com, support@ip2location.com
+Copyright (C) 2019 by IP2Location.com, support@ip2location.com
diff --git a/ip2location.go b/ip2location.go
index 810d9cc..cb45067 100644
--- a/ip2location.go
+++ b/ip2location.go
@@ -72,10 +72,17 @@ var mobilebrand_position = [25]uint8{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
 var elevation_position = [25]uint8{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 11, 19, 0, 19}
 var usagetype_position = [25]uint8{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12, 20}
 
-const api_version string = "8.0.3"
+const api_version string = "8.1.0"
 
 var max_ipv4_range = big.NewInt(4294967295)
 var max_ipv6_range = big.NewInt(0)
+var from_v4mapped = big.NewInt(281470681743360)
+var to_v4mapped = big.NewInt(281474976710655)
+var from_6to4 = big.NewInt(0)
+var to_6to4 = big.NewInt(0)
+var from_teredo = big.NewInt(0)
+var to_teredo = big.NewInt(0)
+var last_32bits = big.NewInt(4294967295)
 
 const countryshort uint32 = 0x00001
 const countrylong uint32 = 0x00002
@@ -166,6 +173,22 @@ func checkip(ip string) (iptype uint32, ipnum *big.Int, ipindex uint32) {
 			if v6 != nil {
 				iptype = 6
 				ipnum.SetBytes(v6)
+				
+				if ipnum.Cmp(from_v4mapped) >= 0 && ipnum.Cmp(to_v4mapped) <= 0 {
+					// ipv4-mapped ipv6 should treat as ipv4 and read ipv4 data section
+					iptype = 4
+					ipnum.Sub(ipnum, from_v4mapped)
+				} else if ipnum.Cmp(from_6to4) >= 0 && ipnum.Cmp(to_6to4) <= 0 {
+					// 6to4 so need to remap to ipv4
+					iptype = 4
+					ipnum.Rsh(ipnum, 80)
+					ipnum.And(ipnum, last_32bits)
+				} else if ipnum.Cmp(from_teredo) >= 0 && ipnum.Cmp(to_teredo) <= 0 {
+					// Teredo so need to remap to ipv4
+					iptype = 4
+					ipnum.Not(ipnum)
+					ipnum.And(ipnum, last_32bits)
+				}
 			}
 		}
 	}
@@ -271,6 +294,10 @@ func readfloat(pos uint32) float32 {
 // initialize the component with the database path
 func Open(dbpath string) {
 	max_ipv6_range.SetString("340282366920938463463374607431768211455", 10)
+	from_6to4.SetString("42545680458834377588178886921629466624", 10)
+	to_6to4.SetString("42550872755692912415807417417958686719", 10)
+	from_teredo.SetString("42540488161975842760550356425300246528", 10)
+	to_teredo.SetString("42540488241204005274814694018844196863", 10)
 	
 	var err error
 	f, err = os.Open(dbpath)
@@ -563,7 +590,7 @@ func query(ipaddress string, mode uint32) IP2Locationrecord {
 	}
 	
 	if ipno.Cmp(maxip)>=0 {
-		ipno = ipno.Sub(ipno, big.NewInt(1))
+		ipno.Sub(ipno, big.NewInt(1))
 	}
 	
 	for low <= high {