diff --git a/backend/pcloud/pcloud.go b/backend/pcloud/pcloud.go
index 36caf7bf3..3cb0d3aed 100644
--- a/backend/pcloud/pcloud.go
+++ b/backend/pcloud/pcloud.go
@@ -1137,7 +1137,7 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 	// opts.Body=0), so upload it as a multipart form POST with
 	// Content-Length set.
 	if size == 0 {
-		formReader, contentType, overhead, err := rest.MultipartUpload(in, opts.Parameters, "content", leaf)
+		formReader, contentType, overhead, err := rest.MultipartUpload(ctx, in, opts.Parameters, "content", leaf)
 		if err != nil {
 			return errors.Wrap(err, "failed to make multipart upload for 0 length file")
 		}
diff --git a/backend/seafile/webapi.go b/backend/seafile/webapi.go
index f91a9ae2b..563cd1896 100644
--- a/backend/seafile/webapi.go
+++ b/backend/seafile/webapi.go
@@ -682,7 +682,7 @@ func (f *Fs) upload(ctx context.Context, in io.Reader, uploadLink, filePath stri
 		"need_idx_progress": {"true"},
 		"replace":           {"1"},
 	}
-	formReader, contentType, _, err := rest.MultipartUpload(in, parameters, "file", f.opt.Enc.FromStandardName(filename))
+	formReader, contentType, _, err := rest.MultipartUpload(ctx, in, parameters, "file", f.opt.Enc.FromStandardName(filename))
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to make multipart upload")
 	}
diff --git a/backend/zoho/zoho.go b/backend/zoho/zoho.go
index c68c170b3..f8a325469 100644
--- a/backend/zoho/zoho.go
+++ b/backend/zoho/zoho.go
@@ -647,7 +647,7 @@ func (f *Fs) upload(ctx context.Context, name string, parent string, size int64,
 	params.Set("filename", name)
 	params.Set("parent_id", parent)
 	params.Set("override-name-exist", strconv.FormatBool(true))
-	formReader, contentType, overhead, err := rest.MultipartUpload(in, nil, "content", name)
+	formReader, contentType, overhead, err := rest.MultipartUpload(ctx, in, nil, "content", name)
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to make multipart upload")
 	}
diff --git a/fs/operations/rc_test.go b/fs/operations/rc_test.go
index bf42a6f65..5420f3148 100644
--- a/fs/operations/rc_test.go
+++ b/fs/operations/rc_test.go
@@ -450,6 +450,7 @@ func TestRcFsInfo(t *testing.T) {
 func TestUploadFile(t *testing.T) {
 	r, call := rcNewRun(t, "operations/uploadfile")
 	defer r.Finalise()
+	ctx := context.Background()
 
 	testFileName := "test.txt"
 	testFileContent := "Hello World"
@@ -460,7 +461,7 @@ func TestUploadFile(t *testing.T) {
 	currentFile, err := os.Open(path.Join(r.LocalName, testFileName))
 	require.NoError(t, err)
 
-	formReader, contentType, _, err := rest.MultipartUpload(currentFile, url.Values{}, "file", testFileName)
+	formReader, contentType, _, err := rest.MultipartUpload(ctx, currentFile, url.Values{}, "file", testFileName)
 	require.NoError(t, err)
 
 	httpReq := httptest.NewRequest("POST", "/", formReader)
@@ -482,7 +483,7 @@ func TestUploadFile(t *testing.T) {
 	currentFile, err = os.Open(path.Join(r.LocalName, testFileName))
 	require.NoError(t, err)
 
-	formReader, contentType, _, err = rest.MultipartUpload(currentFile, url.Values{}, "file", testFileName)
+	formReader, contentType, _, err = rest.MultipartUpload(ctx, currentFile, url.Values{}, "file", testFileName)
 	require.NoError(t, err)
 
 	httpReq = httptest.NewRequest("POST", "/", formReader)
diff --git a/lib/rest/rest.go b/lib/rest/rest.go
index e72275a73..4490d617a 100644
--- a/lib/rest/rest.go
+++ b/lib/rest/rest.go
@@ -308,7 +308,7 @@ func (api *Client) Call(ctx context.Context, opts *Opts) (resp *http.Response, e
 // the int64 returned is the overhead in addition to the file contents, in case Content-Length is required
 //
 // NB This doesn't allow setting the content type of the attachment
-func MultipartUpload(in io.Reader, params url.Values, contentName, fileName string) (io.ReadCloser, string, int64, error) {
+func MultipartUpload(ctx context.Context, in io.Reader, params url.Values, contentName, fileName string) (io.ReadCloser, string, int64, error) {
 	bodyReader, bodyWriter := io.Pipe()
 	writer := multipart.NewWriter(bodyWriter)
 	contentType := writer.FormDataContentType()
@@ -343,8 +343,21 @@ func MultipartUpload(in io.Reader, params url.Values, contentName, fileName stri
 
 	multipartLength := int64(buf.Len())
 
+	// Make sure we close the pipe writer to release the reader on context cancel
+	quit := make(chan struct{})
+	go func() {
+		select {
+		case <-quit:
+			break
+		case <-ctx.Done():
+			_ = bodyWriter.CloseWithError(ctx.Err())
+		}
+	}()
+
 	// Pump the data in the background
 	go func() {
+		defer close(quit)
+
 		var err error
 
 		for key, vals := range params {
@@ -452,7 +465,7 @@ func (api *Client) callCodec(ctx context.Context, opts *Opts, request interface{
 		opts = opts.Copy()
 
 		var overhead int64
-		opts.Body, opts.ContentType, overhead, err = MultipartUpload(opts.Body, params, opts.MultipartContentName, opts.MultipartFileName)
+		opts.Body, opts.ContentType, overhead, err = MultipartUpload(ctx, opts.Body, params, opts.MultipartContentName, opts.MultipartFileName)
 		if err != nil {
 			return nil, err
 		}