diff --git a/backend/jottacloud/jottacloud.go b/backend/jottacloud/jottacloud.go
index aad41a422..6af70b99b 100644
--- a/backend/jottacloud/jottacloud.go
+++ b/backend/jottacloud/jottacloud.go
@@ -34,6 +34,7 @@ import (
 	"github.com/rclone/rclone/fs/hash"
 	"github.com/rclone/rclone/fs/list"
 	"github.com/rclone/rclone/lib/encoder"
+	"github.com/rclone/rclone/lib/multipart"
 	"github.com/rclone/rclone/lib/oauthutil"
 	"github.com/rclone/rclone/lib/pacer"
 	"github.com/rclone/rclone/lib/rest"
@@ -1924,8 +1925,9 @@ func readMD5(in io.Reader, size, threshold int64) (md5sum string, out io.Reader,
 	// nothing to clean up by default
 	cleanup = func() {}
 
-	// don't cache small files on disk to reduce wear of the disk
-	if size > threshold {
+	// don't cache small files on disk to reduce wear of the disk, but
+	// spool unknown sized streams there as they can't be bounded in memory
+	if size > threshold || size < 0 {
 		var tempFile *os.File
 
 		// create the cache file
@@ -1955,15 +1957,15 @@ func readMD5(in io.Reader, size, threshold int64) (md5sum string, out io.Reader,
 		// replace the already read source with a reader of our cached file
 		out = tempFile
 	} else {
-		// that's a small file, just read it into memory
-		var inData []byte
-		inData, err = io.ReadAll(teeReader)
-		if err != nil {
+		// that's a small file, just read it into memory from the global pool
+		rw := multipart.NewRW()
+		cleanup = func() {
+			_ = rw.Close()
+		}
+		if _, err = io.Copy(rw, teeReader); err != nil {
 			return
 		}
-
-		// set the reader to our read memory block
-		out = bytes.NewReader(inData)
+		out = rw
 	}
 	return hex.EncodeToString(md5Hasher.Sum(nil)), out, cleanup, nil
 }
diff --git a/backend/jottacloud/jottacloud_internal_test.go b/backend/jottacloud/jottacloud_internal_test.go
index db9d6a157..1889400c1 100644
--- a/backend/jottacloud/jottacloud_internal_test.go
+++ b/backend/jottacloud/jottacloud_internal_test.go
@@ -5,12 +5,14 @@ import (
 	"crypto/md5"
 	"fmt"
 	"io"
+	"os"
 	"testing"
 	"time"
 
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fstest"
 	"github.com/rclone/rclone/fstest/fstests"
+	"github.com/rclone/rclone/lib/pool"
 	"github.com/rclone/rclone/lib/random"
 	"github.com/rclone/rclone/lib/readers"
 	"github.com/stretchr/testify/assert"
@@ -28,11 +30,16 @@ func TestReadMD5(t *testing.T) {
 			wantMD5 := fmt.Sprintf("%x", hasher.Sum(nil))
 			for _, threshold := range []int64{512, 1024, 10 * 1024, 20 * 1024} {
 				t.Run(fmt.Sprintf("%d", threshold), func(t *testing.T) {
+					inUse := pool.Global().InUse()
 					in := readers.NewPatternReader(size)
 					gotMD5, out, cleanup, err := readMD5(in, size, threshold)
-					defer cleanup()
 					require.NoError(t, err)
 					assert.Equal(t, wantMD5, gotMD5)
+					if size > threshold {
+						assert.IsType(t, (*os.File)(nil), out, "big files should be spooled to disk")
+					} else {
+						assert.IsType(t, (*pool.RW)(nil), out, "small files should be buffered in the pool")
+					}
 
 					// check md5hash of out
 					hasher := md5.New()
@@ -41,10 +48,36 @@ func TestReadMD5(t *testing.T) {
 					assert.Equal(t, n, size)
 					outMD5 := fmt.Sprintf("%x", hasher.Sum(nil))
 					assert.Equal(t, wantMD5, outMD5)
+
+					// check cleanup returns the buffer to the pool
+					cleanup()
+					assert.Equal(t, inUse, pool.Global().InUse(), "pool buffers leaked")
 				})
 			}
 		})
 	}
+
+	// Unknown sized streams can't be bounded in memory so must be spooled to disk
+	t.Run("UnknownSize", func(t *testing.T) {
+		const size = 1024
+		inUse := pool.Global().InUse()
+		hasher := md5.New()
+		_, err := io.Copy(hasher, readers.NewPatternReader(size))
+		require.NoError(t, err)
+		wantMD5 := fmt.Sprintf("%x", hasher.Sum(nil))
+
+		gotMD5, out, cleanup, err := readMD5(readers.NewPatternReader(size), -1, 10*size)
+		require.NoError(t, err)
+		assert.Equal(t, wantMD5, gotMD5)
+		assert.IsType(t, (*os.File)(nil), out)
+		hasher.Reset()
+		n, err := io.Copy(hasher, out)
+		require.NoError(t, err)
+		assert.Equal(t, int64(size), n)
+		assert.Equal(t, wantMD5, fmt.Sprintf("%x", hasher.Sum(nil)))
+		cleanup()
+		assert.Equal(t, inUse, pool.Global().InUse())
+	})
 }
 
 func (f *Fs) InternalTestMetadata(t *testing.T) {