diff --git a/s3/backend.go b/s3/backend.go
index 9f6c8beef..e78ab9cfd 100644
--- a/s3/backend.go
+++ b/s3/backend.go
@@ -401,7 +401,7 @@ func (s *s3) CreateMultipartUpload(ctx context.Context, bucket, key string, meta
 }
 
 func (s *s3) UploadPart(ctx context.Context, bucket, object string, id gofakes3.UploadID, partNumber int, contentLength int64, input io.Reader) (*gofakes3.UploadPartResult, error) {
-	res, err := s.w.UploadMultipartUploadPart(ctx, input, bucket, object, string(id), partNumber, api.UploadMultipartUploadPartOptions{
+	res, err := s.w.UploadMultipartUploadPart(ctx, input, bucket, object, string(id), partNumber, contentLength, api.UploadMultipartUploadPartOptions{
 		DisablePreshardingEncryption: true,
 	})
 	if err != nil {
diff --git a/s3/s3.go b/s3/s3.go
index dc7ac664b..23ecc06c5 100644
--- a/s3/s3.go
+++ b/s3/s3.go
@@ -49,7 +49,7 @@ type bus interface {
 type worker interface {
 	GetObject(ctx context.Context, bucket, path string, opts api.DownloadObjectOptions) (*api.GetObjectResponse, error)
 	UploadObject(ctx context.Context, r io.Reader, bucket, path string, opts api.UploadObjectOptions) (*api.UploadObjectResponse, error)
-	UploadMultipartUploadPart(ctx context.Context, r io.Reader, bucket, path, uploadID string, partNumber int, opts api.UploadMultipartUploadPartOptions) (*api.UploadMultipartUploadPartResponse, error)
+	UploadMultipartUploadPart(ctx context.Context, r io.Reader, bucket, path, uploadID string, partNumber int, contentLength int64, opts api.UploadMultipartUploadPartOptions) (*api.UploadMultipartUploadPartResponse, error)
 }
 
 func (l *gofakes3Logger) Print(level gofakes3.LogLevel, v ...interface{}) {
diff --git a/worker/client/client.go b/worker/client/client.go
index 048ce225c..fcb8f261f 100644
--- a/worker/client/client.go
+++ b/worker/client/client.go
@@ -174,7 +174,7 @@ func (c *Client) State() (state api.WorkerStateResponse, err error) {
 }
 
 // UploadMultipartUploadPart uploads part of the data for a multipart upload.
-func (c *Client) UploadMultipartUploadPart(ctx context.Context, r io.Reader, bucket, path, uploadID string, partNumber int, opts api.UploadMultipartUploadPartOptions) (*api.UploadMultipartUploadPartResponse, error) {
+func (c *Client) UploadMultipartUploadPart(ctx context.Context, r io.Reader, bucket, path, uploadID string, partNumber int, contentLength int64, opts api.UploadMultipartUploadPartOptions) (*api.UploadMultipartUploadPartResponse, error) {
 	path = api.ObjectPathEscape(path)
 	c.c.Custom("PUT", fmt.Sprintf("/multipart/%s", path), []byte{}, nil)
 
@@ -194,6 +194,7 @@ func (c *Client) UploadMultipartUploadPart(ctx context.Context, r io.Reader, buc
 		panic(err)
 	}
 	req.SetBasicAuth("", c.c.WithContext(ctx).Password)
+	req.Header.Add("X-Content-Length", fmt.Sprintf("%d", contentLength))
 	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
 		return nil, err