diff --git a/src/restic/repository/config.go b/src/restic/repository/config.go
index abe1277ed..46f739d35 100644
--- a/src/restic/repository/config.go
+++ b/src/restic/repository/config.go
@@ -6,6 +6,7 @@ import (
 	"encoding/hex"
 	"errors"
 	"io"
+	"testing"
 
 	"restic/backend"
 	"restic/debug"
@@ -63,6 +64,22 @@ func CreateConfig() (Config, error) {
 	return cfg, nil
 }
 
+// TestCreateConfig creates a config for use within tests.
+func TestCreateConfig(t testing.TB, pol chunker.Pol) (cfg Config) {
+	cfg.ChunkerPolynomial = pol
+
+	newID := make([]byte, repositoryIDSize)
+	_, err := io.ReadFull(rand.Reader, newID)
+	if err != nil {
+		t.Fatalf("unable to create random ID: %v", err)
+	}
+
+	cfg.ID = hex.EncodeToString(newID)
+	cfg.Version = RepoVersion
+
+	return cfg
+}
+
 // LoadConfig returns loads, checks and returns the config for a repository.
 func LoadConfig(r JSONUnpackedLoader) (Config, error) {
 	var (
diff --git a/src/restic/repository/testing.go b/src/restic/repository/testing.go
index f45714d80..f0a9913f1 100644
--- a/src/restic/repository/testing.go
+++ b/src/restic/repository/testing.go
@@ -6,6 +6,8 @@ import (
 	"restic/backend/local"
 	"restic/backend/mem"
 	"testing"
+
+	"github.com/restic/chunker"
 )
 
 // TestBackend returns a fully configured in-memory backend.
@@ -16,8 +18,11 @@ func TestBackend(t testing.TB) (be backend.Backend, cleanup func()) {
 // TestPassword is used for all repositories created by the Test* functions.
 const TestPassword = "geheim"
 
+const testChunkerPol = chunker.Pol(0x3DA3358B4DC173)
+
 // TestRepositoryWithBackend returns a repository initialized with a test
-// password. If be is nil, an in-memory backend is used.
+// password. If be is nil, an in-memory backend is used. A constant polynomial
+// is used for the chunker.
 func TestRepositoryWithBackend(t testing.TB, be backend.Backend) (r *Repository, cleanup func()) {
 	var beCleanup func()
 	if be == nil {
@@ -26,9 +31,10 @@ func TestRepositoryWithBackend(t testing.TB, be backend.Backend) (r *Repository,
 
 	r = New(be)
 
-	err := r.Init(TestPassword)
+	cfg := TestCreateConfig(t, testChunkerPol)
+	err := r.init(TestPassword, cfg)
 	if err != nil {
-		t.Fatalf("TestRepopository(): initialize repo failed: %v", err)
+		t.Fatalf("TestRepository(): initialize repo failed: %v", err)
 	}
 
 	return r, func() {
@@ -41,7 +47,7 @@ func TestRepositoryWithBackend(t testing.TB, be backend.Backend) (r *Repository,
 // TestRepository returns a repository initialized with a test password on an
 // in-memory backend. When the environment variable RESTIC_TEST_REPO is set to
 // a non-existing directory, a local backend is created there and this is used
-// instead. The directory is not removed.
+// instead. The directory is not removed, but left there for inspection.
 func TestRepository(t testing.TB) (r *Repository, cleanup func()) {
 	dir := os.Getenv("RESTIC_TEST_REPO")
 	if dir != "" {