diff --git a/modload/module.go b/modload/module.go
index f20d6be..ce70824 100644
--- a/modload/module.go
+++ b/modload/module.go
@@ -204,16 +204,18 @@ func LoadFromEx(gomod, gopmod string, readFile func(string) ([]byte, error)) (p
 	}
 
 	var opt *modfile.File
-	data, err = readFile(gopmod)
-	if err != nil {
-		opt = newGopMod(gopmod, defaultGopVer)
-	} else {
-		opt, err = modfile.ParseLax(gopmod, data, fix)
-		if err != nil {
-			err = errors.NewWith(err, `modfile.Parse(gopmod, data, fix)`, -2, "modfile.Parse", gopmod, data, fix)
-			return
+	if gopmod != "" {
+		if data, err = readFile(gopmod); err == nil {
+			opt, err = modfile.ParseLax(gopmod, data, fix)
+			if err != nil {
+				err = errors.NewWith(err, `modfile.Parse(gopmod, data, fix)`, -2, "modfile.Parse", gopmod, data, fix)
+				return
+			}
 		}
 	}
+	if opt == nil {
+		opt = newGopMod(gopmod, defaultGopVer)
+	}
 	importClassfileFromGoMod(opt, f)
 	return Module{f, opt}, nil
 }
@@ -300,13 +302,46 @@ func (p Module) Save() (err error) {
 	return
 }
 
+func (p Module) checkGopDeps() (flags int) {
+	for _, r := range p.File.Require {
+		switch r.Mod.Path {
+		case gopMod:
+			flags |= FlagDepModGop
+		case xMod:
+			flags |= FlagDepModX
+		}
+	}
+	return
+}
+
+func findReplaceGopMod(work *gomodfile.WorkFile) bool {
+	for _, r := range work.Replace {
+		if r.Old.Path == gopMod {
+			return true
+		}
+	}
+	return false
+}
+
+const (
+	gopMod = "github.com/goplus/gop"
+	xMod   = "github.com/qiniu/x"
+)
+
+const (
+	FlagDepModGop = 1 << iota // depends module github.com/goplus/gop
+	FlagDepModX               // depends module github.com/qiniu/x
+)
+
 // SaveWithGopMod adds `require github.com/goplus/gop` and saves all
 // changes of this module.
 func (p Module) SaveWithGopMod(gop *env.Gop, flags int) (err error) {
 	gopVer := getGopVer(gop)
-	p.requireGop(gop, gopVer, flags)
-	if err = p.Save(); err != nil {
-		return
+	if old := p.checkGopDeps(); old != flags {
+		p.requireGop(gop, gopVer, old, flags)
+		if err = p.Save(); err != nil {
+			return
+		}
 	}
 
 	var work *gomodfile.WorkFile
@@ -324,14 +359,34 @@ func (p Module) SaveWithGopMod(gop *env.Gop, flags int) (err error) {
 	if work, err = gomodfile.ParseWork(workFile, b, fix); err != nil {
 		return
 	}
-	work.AddReplace("github.com/goplus/gop", gopVer, gop.Root, "")
+	if findReplaceGopMod(work) {
+		return
+	}
+	work.AddReplace(gopMod, gopVer, gop.Root, "")
 	return os.WriteFile(workFile, gomodfile.Format(work.Syntax), 0666)
 }
 
 // requireGop adds require for the github.com/goplus/gop module.
-func (p Module) requireGop(gop *env.Gop, gopVer string, flags int) {
-	p.File.AddRequire("github.com/goplus/gop", gopVer)
-	// TODO: AddRequire "github.com/qiniu/x" if necessary
+func (p Module) requireGop(gop *env.Gop, gopVer string, old, flags int) {
+	if (flags&FlagDepModGop) != 0 && (old&FlagDepModGop) == 0 {
+		p.File.AddRequire(gopMod, gopVer)
+	}
+	if (flags&FlagDepModX) != 0 && (old&FlagDepModX) == 0 { // depends module github.com/qiniu/x
+		if x, ok := getXVer(gop); ok {
+			p.File.AddRequire(x.Path, x.Version)
+		}
+	}
+}
+
+func getXVer(gop *env.Gop) (modVer module.Version, ok bool) {
+	if mod, err := LoadFrom(gop.Root+"/go.mod", ""); err == nil {
+		for _, r := range mod.File.Require {
+			if r.Mod.Path == xMod {
+				return r.Mod, true
+			}
+		}
+	}
+	return
 }
 
 func getGopVer(gop *env.Gop) string {
diff --git a/modload/module_test.go b/modload/module_test.go
index 40a0da7..79b4143 100644
--- a/modload/module_test.go
+++ b/modload/module_test.go
@@ -18,6 +18,7 @@ package modload
 
 import (
 	"encoding/json"
+	"log"
 	"os"
 	"runtime"
 	"testing"
@@ -145,7 +146,7 @@ func TestSaveDefault(t *testing.T) {
 
 func TestSave(t *testing.T) {
 	dir := ".gop/_tempdir"
-	os.RemoveAll(dir)
+	os.RemoveAll(".gop")
 	os.MkdirAll(dir, 0777)
 	mod, err := Create(dir, "github.com/foo/bar", "", "")
 	if err != nil {
@@ -160,7 +161,7 @@ func TestSave(t *testing.T) {
 	if err != nil {
 		t.Fatal("Load:", err)
 	}
-	if err = mod.SaveWithGopMod(&env.Gop{Version: "v1.2.0 devel", Root: "/foo/bar/gop"}, 0); err != nil {
+	if err = mod.SaveWithGopMod(&env.Gop{Version: "v1.2.0 devel", Root: "/foo/bar/gop"}, FlagDepModGop); err != nil {
 		t.Fatal("mod.SaveWithGopMod:", err)
 	}
 	if b, err := mod.File.Format(); err != nil {
@@ -186,6 +187,43 @@ replace github.com/goplus/gop v1.2.0 => /foo/bar/gop
 ` {
 		t.Fatal("workFile:", v)
 	}
+
+	// SaveWithGopMod with FlagDepModX
+	os.WriteFile(".gop/go.mod", []byte(`
+module github.com/goplus/gop
+
+go 1.18
+
+require (
+	github.com/qiniu/x v1.13.0
+)
+`), 0666)
+	if err = mod.SaveWithGopMod(&env.Gop{Version: "v1.2.0 devel", Root: ".gop"}, FlagDepModGop|FlagDepModX); err != nil {
+		t.Fatal("mod.SaveWithGopMod 2:", err)
+	}
+	if b, err := mod.File.Format(); err != nil {
+		t.Fatal("Format:", err)
+	} else if v := string(b); v != `module github.com/foo/bar
+
+go 1.18
+
+require (
+	github.com/goplus/yap v0.5.0 //gop:class
+	github.com/goplus/gop v1.2.0
+	github.com/qiniu/x v1.13.0
+)
+` {
+		t.Fatal("SaveWithGopMod:", v)
+	}
+	if _, ok := getXVer(&env.Gop{Root: "/foo/bar"}); ok {
+		t.Fatal("getXVer: ok?")
+	}
+
+	// SaveWithGopMod again. noop.
+	if err = mod.SaveWithGopMod(&env.Gop{Version: "v1.2.0 devel", Root: ".gop"}, FlagDepModGop|FlagDepModX); err != nil {
+		log.Fatal("mod.SaveWithGopMod 3:", err)
+	}
+
 	mod.Opt.Projects = append(mod.Opt.Projects, spxProject)
 	mod.Save()
 	b, err = os.ReadFile(mod.Opt.Syntax.Name)