diff --git a/cmd/gomobile/bind.go b/cmd/gomobile/bind.go
index 2910d8d..e26d51e 100644
--- a/cmd/gomobile/bind.go
+++ b/cmd/gomobile/bind.go
@@ -18,8 +18,6 @@ import (
 	"golang.org/x/tools/go/packages"
 )
 
-// ctx in build.go
-
 var cmdBind = &command{
 	run:   runBind,
 	Name:  "bind",
@@ -81,12 +79,6 @@ func runBind(cmd *command) error {
 		return fmt.Errorf(`invalid -target=%q: %v`, buildTarget, err)
 	}
 
-	// TODO(hajimehoshi): ctx is now used only for recording build tags in bind. Remove this.
-	oldCtx := ctx
-	defer func() {
-		ctx = oldCtx
-	}()
-
 	if bindJavaPkg != "" && targetOS != "android" {
 		return fmt.Errorf("-javapkg is supported only for android target")
 	}
@@ -99,9 +91,6 @@ func runBind(cmd *command) error {
 			return err
 		}
 	}
-	if targetOS == "darwin" {
-		ctx.BuildTags = append(ctx.BuildTags, "ios")
-	}
 
 	var gobind string
 	if !buildN {
@@ -232,8 +221,12 @@ func writeFile(filename string, generate func(io.Writer) error) error {
 func packagesConfig(targetOS string) *packages.Config {
 	config := &packages.Config{}
 	config.Env = append(os.Environ(), "GOARCH=arm", "GOOS="+targetOS)
-	if len(ctx.BuildTags) > 0 {
-		config.BuildFlags = []string{"-tags=" + strings.Join(ctx.BuildTags, ",")}
+	tags := buildTags
+	if targetOS == "darwin" {
+		tags = append(tags, "ios")
+	}
+	if len(tags) > 0 {
+		config.BuildFlags = []string{"-tags=" + strings.Join(tags, ",")}
 	}
 	return config
 }
diff --git a/cmd/gomobile/bind_androidapp.go b/cmd/gomobile/bind_androidapp.go
index 8bba0da..f2f36b4 100644
--- a/cmd/gomobile/bind_androidapp.go
+++ b/cmd/gomobile/bind_androidapp.go
@@ -31,8 +31,8 @@ func goAndroidBind(gobind string, pkgs []*packages.Package, androidArchs []strin
 	)
 	cmd.Env = append(cmd.Env, "GOOS=android")
 	cmd.Env = append(cmd.Env, "CGO_ENABLED=1")
-	if len(ctx.BuildTags) > 0 {
-		cmd.Args = append(cmd.Args, "-tags="+strings.Join(ctx.BuildTags, ","))
+	if len(buildTags) > 0 {
+		cmd.Args = append(cmd.Args, "-tags="+strings.Join(buildTags, ","))
 	}
 	if bindJavaPkg != "" {
 		cmd.Args = append(cmd.Args, "-javapkg="+bindJavaPkg)
diff --git a/cmd/gomobile/bind_iosapp.go b/cmd/gomobile/bind_iosapp.go
index 69a1636..53b5591 100644
--- a/cmd/gomobile/bind_iosapp.go
+++ b/cmd/gomobile/bind_iosapp.go
@@ -24,9 +24,8 @@ func goIOSBind(gobind string, pkgs []*packages.Package, archs []string) error {
 	)
 	cmd.Env = append(cmd.Env, "GOOS=darwin")
 	cmd.Env = append(cmd.Env, "CGO_ENABLED=1")
-	if len(ctx.BuildTags) > 0 {
-		cmd.Args = append(cmd.Args, "-tags="+strings.Join(ctx.BuildTags, ","))
-	}
+	tags := append(buildTags, "ios")
+	cmd.Args = append(cmd.Args, "-tags="+strings.Join(tags, ","))
 	if bindPrefix != "" {
 		cmd.Args = append(cmd.Args, "-prefix="+bindPrefix)
 	}
diff --git a/cmd/gomobile/build.go b/cmd/gomobile/build.go
index 59aa286..208a174 100644
--- a/cmd/gomobile/build.go
+++ b/cmd/gomobile/build.go
@@ -9,7 +9,6 @@ package main
 import (
 	"bufio"
 	"fmt"
-	"go/build"
 	"io"
 	"os"
 	"os/exec"
@@ -20,7 +19,6 @@ import (
 	"golang.org/x/tools/go/packages"
 )
 
-var ctx = build.Default
 var tmpdir string
 
 var cmdBuild = &command{
@@ -89,16 +87,6 @@ func runBuildImpl(cmd *command) (*packages.Package, error) {
 		return nil, fmt.Errorf(`invalid -target=%q: %v`, buildTarget, err)
 	}
 
-	// TODO(hajimehoshi): ctx is now used only for recording build tags in build. Remove this.
-	oldCtx := ctx
-	defer func() {
-		ctx = oldCtx
-	}()
-
-	if targetOS == "darwin" {
-		ctx.BuildTags = append(ctx.BuildTags, "ios")
-	}
-
 	var buildPath string
 	switch len(args) {
 	case 0:
@@ -228,20 +216,21 @@ func printcmd(format string, args ...interface{}) {
 
 // "Build flags", used by multiple commands.
 var (
-	buildA          bool   // -a
-	buildI          bool   // -i
-	buildN          bool   // -n
-	buildV          bool   // -v
-	buildX          bool   // -x
-	buildO          string // -o
-	buildGcflags    string // -gcflags
-	buildLdflags    string // -ldflags
-	buildTarget     string // -target
-	buildTrimpath   bool   // -trimpath
-	buildWork       bool   // -work
-	buildBundleID   string // -bundleid
-	buildIOSVersion string // -iosversion
-	buildAndroidAPI int    // -androidapi
+	buildA          bool        // -a
+	buildI          bool        // -i
+	buildN          bool        // -n
+	buildV          bool        // -v
+	buildX          bool        // -x
+	buildO          string      // -o
+	buildGcflags    string      // -gcflags
+	buildLdflags    string      // -ldflags
+	buildTarget     string      // -target
+	buildTrimpath   bool        // -trimpath
+	buildWork       bool        // -work
+	buildBundleID   string      // -bundleid
+	buildIOSVersion string      // -iosversion
+	buildAndroidAPI int         // -androidapi
+	buildTags       stringsFlag // -tags
 )
 
 func addBuildFlags(cmd *command) {
@@ -256,7 +245,7 @@ func addBuildFlags(cmd *command) {
 	cmd.flag.BoolVar(&buildA, "a", false, "")
 	cmd.flag.BoolVar(&buildI, "i", false, "")
 	cmd.flag.BoolVar(&buildTrimpath, "trimpath", false, "")
-	cmd.flag.Var((*stringsFlag)(&ctx.BuildTags), "tags", "")
+	cmd.flag.Var(&buildTags, "tags", "")
 }
 
 func addBuildFlagsNVXWork(cmd *command) {
@@ -299,8 +288,16 @@ func goCmd(subcmd string, srcs []string, env []string, args ...string) error {
 		goBin(),
 		subcmd,
 	)
-	if len(ctx.BuildTags) > 0 {
-		cmd.Args = append(cmd.Args, "-tags", strings.Join(ctx.BuildTags, " "))
+	tags := buildTags
+	targetOS, _, err := parseBuildTarget(buildTarget)
+	if err != nil {
+		return err
+	}
+	if targetOS == "darwin" {
+		tags = append(tags, "ios")
+	}
+	if len(tags) > 0 {
+		cmd.Args = append(cmd.Args, "-tags", strings.Join(tags, " "))
 	}
 	if buildV {
 		cmd.Args = append(cmd.Args, "-v")
diff --git a/cmd/gomobile/build_darwin_test.go b/cmd/gomobile/build_darwin_test.go
index 0b25d2a..73e1b81 100644
--- a/cmd/gomobile/build_darwin_test.go
+++ b/cmd/gomobile/build_darwin_test.go
@@ -23,10 +23,10 @@ func TestIOSBuild(t *testing.T) {
 	buildTarget = "ios"
 	buildBundleID = "org.golang.todo"
 	gopath = filepath.SplitList(goEnv("GOPATH"))[0]
-	oldTags := ctx.BuildTags
-	ctx.BuildTags = []string{"tag1"}
+	oldTags := buildTags
+	buildTags = []string{"tag1"}
 	defer func() {
-		ctx.BuildTags = oldTags
+		buildTags = oldTags
 	}()
 	tests := []struct {
 		pkg  string
diff --git a/cmd/gomobile/build_test.go b/cmd/gomobile/build_test.go
index 619a4fa..75c601b 100644
--- a/cmd/gomobile/build_test.go
+++ b/cmd/gomobile/build_test.go
@@ -86,10 +86,10 @@ func TestAndroidBuild(t *testing.T) {
 		os.Setenv("HOMEDRIVE", "C:")
 	}
 	cmdBuild.flag.Parse([]string{"golang.org/x/mobile/example/basic"})
-	oldTags := ctx.BuildTags
-	ctx.BuildTags = []string{"tag1"}
+	oldTags := buildTags
+	buildTags = []string{"tag1"}
 	defer func() {
-		ctx.BuildTags = oldTags
+		buildTags = oldTags
 	}()
 	err := runBuild(cmdBuild)
 	if err != nil {