diff --git a/frontend/dockerfile/builder/build.go b/frontend/dockerfile/builder/build.go
index 76777eea..6af3bab3 100644
--- a/frontend/dockerfile/builder/build.go
+++ b/frontend/dockerfile/builder/build.go
@@ -8,6 +8,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net"
+	"path"
 	"regexp"
 	"strconv"
 	"strings"
@@ -46,6 +47,7 @@ const (
 	keyOverrideCopyImage       = "override-copy-image" // remove after CopyOp implemented
 	keyNameContext             = "contextkey"
 	keyNameDockerfile          = "dockerfilekey"
+	keyContextSubDir           = "contextsubdir"
 )
 
 var httpPrefix = regexp.MustCompile("^https?://")
@@ -122,6 +124,8 @@ func Build(ctx context.Context, c client.Client) (*client.Result, error) {
 		dockerfile2llb.WithInternalName(name),
 	)
 
+	fileop := useFileOp(opts, &caps)
+
 	var buildContext *llb.State
 	isScratchContext := false
 	if st, ok := detectGitContext(opts[localNameContext]); ok {
@@ -157,7 +161,6 @@ func Build(ctx context.Context, c client.Client) (*client.Result, error) {
 			return nil, errors.Errorf("failed to read downloaded context")
 		}
 		if isArchive(dt) {
-			fileop := useFileOp(opts, &caps)
 			if fileop {
 				bc := llb.Scratch().File(llb.Copy(httpContext, "/context", "/", &llb.CopyInfo{
 					AttemptUnpack: true,
@@ -190,6 +193,12 @@ func Build(ctx context.Context, c client.Client) (*client.Result, error) {
 		}
 	}
 
+	if buildContext != nil {
+		if sub, ok := opts[keyContextSubDir]; ok {
+			buildContext = scopeToSubDir(buildContext, fileop, sub)
+		}
+	}
+
 	def, err := src.Marshal(marshalOpts...)
 	if err != nil {
 		return nil, errors.Wrapf(err, "failed to marshal local source")
@@ -561,3 +570,17 @@ func useFileOp(args map[string]string, caps *apicaps.CapSet) bool {
 	}
 	return enabled && caps != nil && caps.Supports(pb.CapFileBase) == nil
 }
+
+func scopeToSubDir(c *llb.State, fileop bool, dir string) *llb.State {
+	if fileop {
+		bc := llb.Scratch().File(llb.Copy(*c, dir, "/", &llb.CopyInfo{
+			CopyDirContentsOnly: true,
+		}))
+		return &bc
+	}
+	unpack := llb.Image(dockerfile2llb.DefaultCopyImage, dockerfile2llb.WithInternalName("helper image for file operations")).
+		Run(llb.Shlexf("copy %s/. /out/", path.Join("/src", dir)), llb.ReadonlyRootFS(), dockerfile2llb.WithInternalName("filtering build context"))
+	unpack.AddMount("/src", *c, llb.Readonly)
+	bc := unpack.AddMount("/out", llb.Scratch())
+	return &bc
+}
diff --git a/frontend/dockerfile/dockerfile_test.go b/frontend/dockerfile/dockerfile_test.go
index cf261a9e..7f71cf95 100644
--- a/frontend/dockerfile/dockerfile_test.go
+++ b/frontend/dockerfile/dockerfile_test.go
@@ -3844,7 +3844,7 @@ func testTarContextExternalDockerfile(t *testing.T, sb integration.Sandbox) {
 	buf := bytes.NewBuffer(nil)
 	tw := tar.NewWriter(buf)
 	err := tw.WriteHeader(&tar.Header{
-		Name:     "foo",
+		Name:     "sub/dir/foo",
 		Typeflag: tar.TypeReg,
 		Size:     int64(len(foo)),
 		Mode:     0644,
@@ -3882,6 +3882,7 @@ COPY foo bar
 			"build-arg:BUILDKIT_DISABLE_FILEOP": strconv.FormatBool(!isFileOp),
 			"context":                           url,
 			"dockerfilekey":                     builder.DefaultLocalNameDockerfile,
+			"contextsubdir":                     "sub/dir",
 		},
 		Session: []session.Attachable{up},
 		LocalDirs: map[string]string{