diff --git a/go.mod b/go.mod
index 83eebc1..db0d4d5 100644
--- a/go.mod
+++ b/go.mod
@@ -6,5 +6,21 @@ require (
 	github.com/cybozu-go/netutil v1.2.0
 	github.com/cybozu-go/well v1.8.1
 	golang.org/x/net v0.0.0-20180911220305-26e67e76b6c3
-	golang.org/x/sys v0.0.0-20180906133057-8cf3aee42992
+	golang.org/x/sys v0.1.0
+)
+
+require (
+	github.com/fsnotify/fsnotify v1.4.7 // indirect
+	github.com/hashicorp/hcl v1.0.0 // indirect
+	github.com/magiconair/properties v1.8.0 // indirect
+	github.com/mitchellh/mapstructure v1.0.0 // indirect
+	github.com/pelletier/go-toml v1.2.0 // indirect
+	github.com/pkg/errors v0.8.0 // indirect
+	github.com/spf13/afero v1.1.2 // indirect
+	github.com/spf13/cast v1.2.0 // indirect
+	github.com/spf13/jwalterweatherman v1.0.0 // indirect
+	github.com/spf13/pflag v1.0.3 // indirect
+	github.com/spf13/viper v1.2.1 // indirect
+	golang.org/x/text v0.3.0 // indirect
+	gopkg.in/yaml.v2 v2.2.1 // indirect
 )