diff --git a/cmd/osbuild-worker/main.go b/cmd/osbuild-worker/main.go
index d4365b583..1913f068e 100644
--- a/cmd/osbuild-worker/main.go
+++ b/cmd/osbuild-worker/main.go
@@ -11,6 +11,7 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"os/exec"
 	"path"
 	"time"
 
@@ -65,6 +66,26 @@ func (e *TargetsError) Error() string {
 	return errString
 }
 
+func openAsStreamOptimizedVmdk(imagePath string) (*os.File, error) {
+	newPath := imagePath + ".stream"
+	cmd := exec.Command(
+		"/usr/bin/qemu-img", "convert", "-O", "vmdk", "-o", "subformat=streamOptimized",
+		imagePath, newPath)
+	err := cmd.Run()
+	if err != nil {
+		return nil, err
+	}
+	f, err := os.Open(newPath)
+	if err != nil {
+		return nil, err
+	}
+	err = os.Remove(newPath)
+	if err != nil {
+		return nil, err
+	}
+	return f, err
+}
+
 func RunJob(job *worker.Job, store string, uploadFunc func(uuid.UUID, string, io.Reader) error) (*common.ComposeResult, error) {
 	outputDirectory, err := ioutil.TempDir("/var/tmp", "osbuild-worker-*")
 	if err != nil {
@@ -87,10 +108,20 @@ func RunJob(job *worker.Job, store string, uploadFunc func(uuid.UUID, string, io
 	for _, t := range job.Targets {
 		switch options := t.Options.(type) {
 		case *target.LocalTargetOptions:
-			f, err := os.Open(path.Join(outputDirectory, options.Filename))
-			if err != nil {
-				r = append(r, err)
-				continue
+			var f *os.File
+			imagePath := path.Join(outputDirectory, options.Filename)
+			if options.StreamOptimized {
+				f, err = openAsStreamOptimizedVmdk(imagePath)
+				if err != nil {
+					r = append(r, err)
+					continue
+				}
+			} else {
+				f, err = os.Open(imagePath)
+				if err != nil {
+					r = append(r, err)
+					continue
+				}
 			}
 
 			err = uploadFunc(job.Id, options.Filename, f)
diff --git a/golang-github-osbuild-composer.spec b/golang-github-osbuild-composer.spec
index 6fa19fd16..b38dae55c 100644
--- a/golang-github-osbuild-composer.spec
+++ b/golang-github-osbuild-composer.spec
@@ -47,6 +47,7 @@ Requires: %{name}-worker = %{version}-%{release}
 Requires: systemd
 Requires: osbuild >= 18
 Requires: osbuild-ostree >= 18
+Requires: qemu-img
 
 Provides: osbuild-composer
 Provides: weldr
diff --git a/internal/target/local_target.go b/internal/target/local_target.go
index 6e57f5d20..49083a84f 100644
--- a/internal/target/local_target.go
+++ b/internal/target/local_target.go
@@ -3,9 +3,10 @@ package target
 import "github.com/google/uuid"
 
 type LocalTargetOptions struct {
-	ComposeId    uuid.UUID `json:"compose_id"`
-	ImageBuildId int       `json:"image_build_id"`
-	Filename     string    `json:"filename"`
+	ComposeId       uuid.UUID `json:"compose_id"`
+	ImageBuildId    int       `json:"image_build_id"`
+	Filename        string    `json:"filename"`
+	StreamOptimized bool      `json:"stream_optimized"` // return image as stream optimized
 }
 
 func (LocalTargetOptions) isTargetOptions() {}
diff --git a/internal/weldr/api.go b/internal/weldr/api.go
index 6a8988377..243242a1b 100644
--- a/internal/weldr/api.go
+++ b/internal/weldr/api.go
@@ -1753,9 +1753,10 @@ func (api *API) composeHandler(writer http.ResponseWriter, request *http.Request
 
 	targets = append(targets, target.NewLocalTarget(
 		&target.LocalTargetOptions{
-			ComposeId:    composeID,
-			ImageBuildId: 0,
-			Filename:     imageType.Filename(),
+			ComposeId:       composeID,
+			ImageBuildId:    0,
+			Filename:        imageType.Filename(),
+			StreamOptimized: imageType.Name() == "vmdk", // TODO: move conversion to osbuild
 		},
 	))
 
diff --git a/osbuild-composer.spec b/osbuild-composer.spec
index 7129640e0..fa6837d96 100644
--- a/osbuild-composer.spec
+++ b/osbuild-composer.spec
@@ -52,6 +52,7 @@ Requires: %{name}-worker = %{version}-%{release}
 Requires: systemd
 Requires: osbuild >= 18
 Requires: osbuild-ostree >= 18
+Requires: qemu-img
 
 Provides: weldr