diff --git a/cmd/test/makefiles/makefiles.go b/cmd/test/makefiles/makefiles.go
index 07db517f2..abbab739d 100644
--- a/cmd/test/makefiles/makefiles.go
+++ b/cmd/test/makefiles/makefiles.go
@@ -3,12 +3,12 @@
 package makefiles
 
 import (
-	cryptrand "crypto/rand"
 	"io"
 	"log"
 	"math/rand"
 	"os"
 	"path/filepath"
+	"time"
 
 	"github.com/rclone/rclone/cmd"
 	"github.com/rclone/rclone/cmd/test"
@@ -27,8 +27,10 @@ var (
 	maxFileSize              = fs.SizeSuffix(100)
 	minFileNameLength        = 4
 	maxFileNameLength        = 12
+	seed                     = int64(1)
 
 	// Globals
+	randSource          *rand.Rand
 	directoriesToCreate int
 	totalDirectories    int
 	fileNames           = map[string]struct{}{} // keep a note of which file name we've used already
@@ -44,6 +46,7 @@ func init() {
 	flags.FVarP(cmdFlags, &maxFileSize, "max-file-size", "", "Maximum size of files to create")
 	flags.IntVarP(cmdFlags, &minFileNameLength, "min-name-length", "", minFileNameLength, "Minimum size of file names")
 	flags.IntVarP(cmdFlags, &maxFileNameLength, "max-name-length", "", maxFileNameLength, "Maximum size of file names")
+	flags.Int64VarP(cmdFlags, &seed, "seed", "", seed, "Seed for the random number generator (0 for random)")
 }
 
 var commandDefinition = &cobra.Command{
@@ -51,6 +54,11 @@ var commandDefinition = &cobra.Command{
 	Short: `Make a random file hierarchy in <dir>`,
 	Run: func(command *cobra.Command, args []string) {
 		cmd.CheckArgs(1, 1, command, args)
+		if seed == 0 {
+			seed = time.Now().UnixNano()
+			log.Printf("Using random seed = %d", seed)
+		}
+		randSource = rand.New(rand.NewSource(seed))
 		outputDirectory := args[0]
 		directoriesToCreate = numberOfFiles / averageFilesPerDirectory
 		averageSize := (minFileSize + maxFileSize) / 2
@@ -61,7 +69,7 @@ var commandDefinition = &cobra.Command{
 		}
 		dirs := root.list("", []string{})
 		for i := 0; i < numberOfFiles; i++ {
-			dir := dirs[rand.Intn(len(dirs))]
+			dir := dirs[randSource.Intn(len(dirs))]
 			writeFile(dir, fileName())
 		}
 		log.Printf("Done.")
@@ -71,8 +79,8 @@ var commandDefinition = &cobra.Command{
 // fileName creates a unique random file or directory name
 func fileName() (name string) {
 	for {
-		length := rand.Intn(maxFileNameLength-minFileNameLength) + minFileNameLength
-		name = random.String(length)
+		length := randSource.Intn(maxFileNameLength-minFileNameLength) + minFileNameLength
+		name = random.StringFn(length, randSource.Intn)
 		if _, found := fileNames[name]; !found {
 			break
 		}
@@ -99,7 +107,7 @@ func (d *dir) createDirectories() {
 		}
 		d.children = append(d.children, newDir)
 		totalDirectories++
-		switch rand.Intn(4) {
+		switch randSource.Intn(4) {
 		case 0:
 			if d.depth < maxDepth {
 				newDir.createDirectories()
@@ -132,8 +140,8 @@ func writeFile(dir, name string) {
 	if err != nil {
 		log.Fatalf("Failed to open file %q: %v", path, err)
 	}
-	size := rand.Int63n(int64(maxFileSize-minFileSize)) + int64(minFileSize)
-	_, err = io.CopyN(fd, cryptrand.Reader, size)
+	size := randSource.Int63n(int64(maxFileSize-minFileSize)) + int64(minFileSize)
+	_, err = io.CopyN(fd, randSource, size)
 	if err != nil {
 		log.Fatalf("Failed to write %v bytes to file %q: %v", size, path, err)
 	}
diff --git a/lib/random/random.go b/lib/random/random.go
index 57a858beb..30198bdd4 100644
--- a/lib/random/random.go
+++ b/lib/random/random.go
@@ -10,10 +10,11 @@ import (
 	"github.com/pkg/errors"
 )
 
-// String create a random string for test purposes.
+// StringFn create a random string for test purposes using the random
+// number generator function passed in.
 //
 // Do not use these for passwords.
-func String(n int) string {
+func StringFn(n int, randIntn func(n int) int) string {
 	const (
 		vowel     = "aeiou"
 		consonant = "bcdfghjklmnpqrstvwxyz"
@@ -25,11 +26,18 @@ func String(n int) string {
 	for i := range out {
 		source := pattern[p]
 		p = (p + 1) % len(pattern)
-		out[i] = source[mathrand.Intn(len(source))]
+		out[i] = source[randIntn(len(source))]
 	}
 	return string(out)
 }
 
+// String create a random string for test purposes.
+//
+// Do not use these for passwords.
+func String(n int) string {
+	return StringFn(n, mathrand.Intn)
+}
+
 // Password creates a crypto strong password which is just about
 // memorable.  The password is composed of printable ASCII characters
 // from the base64 alphabet.