diff --git a/.travis.yml b/.travis.yml
index 5232216..4776cd6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,18 +1,10 @@
 language: go
 go:
-- '1.2.x'
-- '1.3.x'
-- '1.4.x'
-- '1.5.x'
-- '1.6.x'
-- '1.7.x'
-- '1.8.x'
-- '1.9.x'
-- '1.10.x'
-- '1.11.x'
-- 'tip'
+  - '1.11.x'
+  - '1.12.x'
+  - 'tip'
 sudo: true
 before_install:
-- ./travis-mecab-install.sh
-- export CGO_LDFLAGS="`mecab-config --libs`"
-- export CGO_CFLAGS="-I`mecab-config --inc-dir`"
+  - ./travis-mecab-install.sh
+  - export CGO_LDFLAGS="`mecab-config --libs`"
+  - export CGO_CFLAGS="-I`mecab-config --inc-dir`"
diff --git a/go.mod b/go.mod
index 9f39e6e..7667a7c 100644
--- a/go.mod
+++ b/go.mod
@@ -1 +1,3 @@
 module github.com/shogo82148/go-mecab
+
+go 1.12
diff --git a/mecab.go b/mecab.go
index 44e470f..36e64a3 100644
--- a/mecab.go
+++ b/mecab.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"reflect"
 	"unsafe"
+	"runtime"
 )
 
 // MeCab is a morphological parser.
@@ -67,6 +68,7 @@ func (m MeCab) Parse(s string) (string, error) {
 	if result == nil {
 		return "", m.Error()
 	}
+	runtime.KeepAlive(s)
 	return C.GoString(result), nil
 }
 
@@ -96,6 +98,7 @@ func (m MeCab) ParseToNode(s string) (Node, error) {
 	if node == nil {
 		return Node{}, m.Error()
 	}
+	runtime.KeepAlive(s)
 	return Node{node: node}, nil
 }