diff --git a/builtin/stringslice/stringslice.go b/builtin/stringslice/stringslice.go
index 32944d997..49306ad06 100644
--- a/builtin/stringslice/stringslice.go
+++ b/builtin/stringslice/stringslice.go
@@ -17,14 +17,14 @@
 package stringslice
 
 import (
-	"github.com/goplus/gop/builtin/strx"
+	"github.com/qiniu/x/stringutil"
 )
 
 // Capitalize capitalizes the first letter of each string in the slice.
 func Capitalize(a []string) []string {
 	r := make([]string, len(a))
 	for i, v := range a {
-		r[i] = strx.Capitalize(v)
+		r[i] = stringutil.Capitalize(v)
 	}
 	return r
 }
diff --git a/builtin/strx/stringutil.go b/builtin/strx/stringutil.go
deleted file mode 100644
index edcead531..000000000
--- a/builtin/strx/stringutil.go
+++ /dev/null
@@ -1,37 +0,0 @@
-/*
- * Copyright (c) 2025 The GoPlus Authors (goplus.org). All rights reserved.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package strx
-
-import (
-	"unicode"
-	"unicode/utf8"
-
-	"github.com/qiniu/x/stringutil"
-)
-
-// Capitalize returns a copy of the string str with the first letter mapped to
-// its upper case.
-func Capitalize(str string) string {
-	c, nc := utf8.DecodeRuneInString(str)
-	if c == utf8.RuneError || unicode.IsUpper(c) {
-		return str
-	}
-	ret := make([]byte, len(str))
-	nr := utf8.EncodeRune(ret, unicode.ToUpper(c))
-	ret = append(ret[:nr], str[nc:]...)
-	return stringutil.String(ret)
-}
diff --git a/cl/builtin.go b/cl/builtin.go
index e0784a102..b0abdcc67 100644
--- a/cl/builtin.go
+++ b/cl/builtin.go
@@ -81,7 +81,7 @@ func newBuiltinDefault(pkg *gogen.Package, conf *gogen.Config) *types.Package {
 	buil := pkg.TryImport("github.com/goplus/gop/builtin")
 	ng := pkg.TryImport("github.com/goplus/gop/builtin/ng")
 	iox := pkg.TryImport("github.com/goplus/gop/builtin/iox")
-	strx := pkg.TryImport("github.com/goplus/gop/builtin/strx")
+	strx := pkg.TryImport("github.com/qiniu/x/stringutil")
 	stringslice := pkg.TryImport("github.com/goplus/gop/builtin/stringslice")
 	pkg.TryImport("strconv")
 	pkg.TryImport("strings")
diff --git a/go.mod b/go.mod
index 524bdfbcb..a060fd1f5 100644
--- a/go.mod
+++ b/go.mod
@@ -7,7 +7,7 @@ require (
 	github.com/goplus/gogen v1.16.6-0.20250112115237-4fcb9989182e
 	github.com/goplus/llgo v0.9.9
 	github.com/goplus/mod v0.13.15
-	github.com/qiniu/x v1.13.10
+	github.com/qiniu/x v1.13.11
 	golang.org/x/tools v0.19.0
 )
 
diff --git a/go.sum b/go.sum
index 80b84e2cc..aaf7fa1bb 100644
--- a/go.sum
+++ b/go.sum
@@ -6,8 +6,8 @@ github.com/goplus/llgo v0.9.9 h1:sCM8ehOtuAEY/NQbJ4xAMRZhxEdDgilouWZpoaLiYrM=
 github.com/goplus/llgo v0.9.9/go.mod h1:udcq+s6tGOdhJq7I8fXPTv4qT2j17/KrlvtcJrMZAoM=
 github.com/goplus/mod v0.13.15 h1:IyneSjwm1VpwvHGz6hSHnFxZCuO6ULHcu74IAZcW9nw=
 github.com/goplus/mod v0.13.15/go.mod h1:invR72Rz2+qpOOsXqxz830MX8/aR2GDR2EAow/WgfHI=
-github.com/qiniu/x v1.13.10 h1:J4Z3XugYzAq85SlyAfqlKVrbf05glMbAOh+QncsDQpE=
-github.com/qiniu/x v1.13.10/go.mod h1:INZ2TSWSJVWO/RuELQROERcslBwVgFG7MkTfEdaQz9E=
+github.com/qiniu/x v1.13.11 h1:zlFLY9zFXOwKEjx0SQXRBunhFjDVpEY+pRGL/4shd5U=
+github.com/qiniu/x v1.13.11/go.mod h1:INZ2TSWSJVWO/RuELQROERcslBwVgFG7MkTfEdaQz9E=
 golang.org/x/mod v0.20.0 h1:utOm6MM3R3dnawAiJgn0y+xvuYRsm1RKM/4giyfDgV0=
 golang.org/x/mod v0.20.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.7.0 h1:YsImfSBoP9QPYL0xyKJPq0gcaJdG3rInoqxTWbfQu9M=