diff --git a/backend/linkbox/linkbox.go b/backend/linkbox/linkbox.go
index a91eb8857..47856f74c 100644
--- a/backend/linkbox/linkbox.go
+++ b/backend/linkbox/linkbox.go
@@ -11,10 +11,10 @@ package linkbox
 */
 
 import (
-	"bytes"
 	"context"
 	"crypto/md5"
 	"crypto/tls"
+	"encoding/hex"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -35,7 +35,9 @@ import (
 	"github.com/rclone/rclone/fs/fshttp"
 	"github.com/rclone/rclone/fs/hash"
 	"github.com/rclone/rclone/lib/dircache"
+	"github.com/rclone/rclone/lib/multipart"
 	"github.com/rclone/rclone/lib/pacer"
+	"github.com/rclone/rclone/lib/pool"
 	"github.com/rclone/rclone/lib/rest"
 )
 
@@ -46,7 +48,8 @@ const (
 	pacerBurst         = 1
 	linkboxAPIURL      = "https://www.linkbox.to/api/open/"
 	linkboxWebAPIURL   = "https://www.linkbox.to/api/"
-	rootID             = "0" // ID of root directory
+	rootID             = "0"              // ID of root directory
+	prefixSize         = 10 * 1024 * 1024 // the API wants the MD5 of the first 10 MiB of a file
 )
 
 func init() {
@@ -667,6 +670,21 @@ func (o *Object) Open(ctx context.Context, options ...fs.OpenOption) (io.ReadClo
 	return res.Body, nil
 }
 
+// readPrefix reads up to prefixSize bytes of in into a buffer from the
+// global pool returning it along with the hex MD5 of what was read.
+//
+// The caller must Close the returned buffer when done with it.
+func readPrefix(in io.Reader) (rw *pool.RW, md5sum string, err error) {
+	rw = multipart.NewRW()
+	hasher := md5.New()
+	_, err = io.CopyN(rw, io.TeeReader(in, hasher), prefixSize)
+	if err != nil && err != io.EOF {
+		_ = rw.Close()
+		return nil, "", err
+	}
+	return rw, hex.EncodeToString(hasher.Sum(nil)), nil
+}
+
 // Update in to the object with the modTime given of the given size
 //
 // When called from outside an Fs by rclone, src.Size() will always be >= 0.
@@ -701,11 +719,13 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 		}
 	}
 
-	first10m := io.LimitReader(in, 10_485_760)
-	first10mBytes, err := io.ReadAll(first10m)
+	prefix, prefixMD5, err := readPrefix(in)
 	if err != nil {
 		return fmt.Errorf("Update err in reading file: %w", err)
 	}
+	defer func() {
+		_ = prefix.Close()
+	}()
 
 	// get upload authorization (step 1)
 	opts := &rest.Opts{
@@ -715,7 +735,7 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 		Options: options,
 		Parameters: url.Values{
 			"token":           {o.fs.opt.Token},
-			"fileMd5ofPre10m": {fmt.Sprintf("%x", md5.Sum(first10mBytes))},
+			"fileMd5ofPre10m": {prefixMD5},
 			"fileSize":        {itoa64(size)},
 		},
 	}
@@ -757,7 +777,7 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 			return fmt.Errorf("head upload URL: %w", err)
 		}
 
-		file := io.MultiReader(bytes.NewReader(first10mBytes), in)
+		file := io.MultiReader(prefix, in)
 
 		opts.Method = "PUT"
 		opts.Body = file
@@ -797,7 +817,7 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 		Options: options,
 		Parameters: url.Values{
 			"token":           {o.fs.opt.Token},
-			"fileMd5ofPre10m": {fmt.Sprintf("%x", md5.Sum(first10mBytes))},
+			"fileMd5ofPre10m": {prefixMD5},
 			"fileSize":        {itoa64(size)},
 			"pid":             {dirID},
 			"diyName":         {leaf},
diff --git a/backend/linkbox/linkbox_internal_test.go b/backend/linkbox/linkbox_internal_test.go
new file mode 100644
index 000000000..588ac6fd8
--- /dev/null
+++ b/backend/linkbox/linkbox_internal_test.go
@@ -0,0 +1,41 @@
+package linkbox
+
+import (
+	"bytes"
+	"crypto/md5"
+	"fmt"
+	"io"
+	"testing"
+
+	"github.com/rclone/rclone/lib/pool"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestReadPrefix(t *testing.T) {
+	for _, size := range []int64{1, 1024, prefixSize - 1, prefixSize, prefixSize + 1, 3 * prefixSize} {
+		t.Run(fmt.Sprintf("%d", size), func(t *testing.T) {
+			inUse := pool.Global().InUse()
+			content := bytes.Repeat([]byte("x"), int(size))
+			for i := range content {
+				content[i] = byte(i)
+			}
+			wantPrefix := content[:min(size, prefixSize)]
+			wantMD5 := fmt.Sprintf("%x", md5.Sum(wantPrefix))
+
+			in := bytes.NewReader(content)
+			rw, gotMD5, err := readPrefix(in)
+			require.NoError(t, err)
+			assert.Equal(t, wantMD5, gotMD5)
+			assert.Equal(t, int64(len(wantPrefix)), rw.Size())
+
+			// The prefix followed by the rest of in must reproduce the content
+			got, err := io.ReadAll(io.MultiReader(rw, in))
+			require.NoError(t, err)
+			assert.Equal(t, content, got)
+
+			require.NoError(t, rw.Close())
+			assert.Equal(t, inUse, pool.Global().InUse(), "pool buffers leaked")
+		})
+	}
+}