diff --git a/cmd/image-builder/repos.go b/cmd/image-builder/repos.go
index 9a357313..ab0e5de7 100644
--- a/cmd/image-builder/repos.go
+++ b/cmd/image-builder/repos.go
@@ -4,26 +4,22 @@ import (
 	"fmt"
 	"io/fs"
 	"net/url"
+	"path/filepath"
 
 	"github.com/osbuild/images/data/repositories"
 	"github.com/osbuild/images/pkg/reporegistry"
 	"github.com/osbuild/images/pkg/rpmmd"
 )
 
-// defaultDataDirs contains the default search paths to look for
+// defaultRepoDirs contains the default search paths to look for
 // repository data. They contain a bunch of json files of the form
 // "$distro_$version".json (but that is an implementation detail that
 // the "images" library takes care of).
-var defaultDataDirs = []string{
+var defaultRepoDirs = []string{
 	"/etc/image-builder/repositories",
 	"/usr/share/image-builder/repositories",
 }
 
-type repoConfig struct {
-	DataDir    string
-	ExtraRepos []string
-}
-
 func parseRepoURLs(repoURLs []string, what string) ([]rpmmd.RepoConfig, error) {
 	var repoConf []rpmmd.RepoConfig
 
@@ -58,14 +54,14 @@ func parseRepoURLs(repoURLs []string, what string) ([]rpmmd.RepoConfig, error) {
 }
 
 func newRepoRegistryImpl(dataDir string, extraRepos []string) (*reporegistry.RepoRegistry, error) {
-	var dataDirs []string
+	var repoDirs []string
 	if dataDir != "" {
-		dataDirs = []string{dataDir}
+		repoDirs = []string{filepath.Join(dataDir, "repositories")}
 	} else {
-		dataDirs = defaultDataDirs
+		repoDirs = defaultRepoDirs
 	}
 
-	conf, err := reporegistry.LoadAllRepositories(dataDirs, []fs.FS{repos.FS})
+	conf, err := reporegistry.LoadAllRepositories(repoDirs, []fs.FS{repos.FS})
 	if err != nil {
 		return nil, err
 	}
diff --git a/cmd/image-builder/repos_test.go b/cmd/image-builder/repos_test.go
index a811b636..bc9d494a 100644
--- a/cmd/image-builder/repos_test.go
+++ b/cmd/image-builder/repos_test.go
@@ -1,9 +1,12 @@
 package main
 
 import (
+	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"github.com/osbuild/images/pkg/rpmmd"
 )
@@ -16,7 +19,7 @@ func TestParseRepoURLsHappy(t *testing.T) {
 		"https://example.com/repo",
 	}, "forced")
 	assert.NoError(t, err)
-	assert.Equal(t, cfg, []rpmmd.RepoConfig{
+	assert.Equal(t, []rpmmd.RepoConfig{
 		{
 			Id:           "forced-repo-0",
 			Name:         "forced repo#0 /path/to/repo",
@@ -31,7 +34,7 @@ func TestParseRepoURLsHappy(t *testing.T) {
 			CheckGPG:     &checkGPG,
 			CheckRepoGPG: &checkGPG,
 		},
-	})
+	}, cfg)
 }
 
 func TestParseExtraRepoSad(t *testing.T) {
@@ -41,3 +44,54 @@ func TestParseExtraRepoSad(t *testing.T) {
 	_, err = parseRepoURLs([]string{"https://example.com", "/just/a/path"}, "forced")
 	assert.EqualError(t, err, `scheme missing in "/just/a/path", please prefix with e.g. file:// or https://`)
 }
+
+func TestNewRepoRegistryImplSmoke(t *testing.T) {
+	registry, err := newRepoRegistryImpl("", nil)
+	require.NoError(t, err)
+	repos, err := registry.DistroHasRepos("rhel-10.2", "x86_64")
+	require.NoError(t, err)
+	assert.True(t, len(repos) > 0)
+}
+
+func TestNewRepoRegistryImplExtraReposGetAppended(t *testing.T) {
+	registry, err := newRepoRegistryImpl("", []string{"https://example.com/my/repo"})
+	require.NoError(t, err)
+	repos, err := registry.DistroHasRepos("rhel-10.2", "x86_64")
+	require.NoError(t, err)
+	assert.Equal(t, repos[len(repos)-1].BaseURLs[0], "https://example.com/my/repo")
+}
+
+func TestNewRepoRegistryImplDatadir(t *testing.T) {
+	// prereq test: no testdistro-1 in the default repos
+	registry, err := newRepoRegistryImpl("", nil)
+	require.NoError(t, err)
+	assert.NotContains(t, registry.ListDistros(), "testdistro-1")
+	_, err = registry.DistroHasRepos("testdistro-1", "x86_64")
+	require.EqualError(t, err, `requested repository not found: for distribution "testdistro-1"`)
+
+	// create a custom datadir with testdistro-1.json, the basefilename
+	// must match a distro nameVer
+	dataDir := t.TempDir()
+	repoFile := filepath.Join(dataDir, "repositories", "testdistro-1.json")
+	err = os.Mkdir(filepath.Dir(repoFile), 0755)
+	require.NoError(t, err)
+	repoContents := `{
+	"x86_64": [
+		{
+			"name": "testdistro-1-repo",
+			"baseurl": "https://example.com/test/test/distro/1"
+		}
+	]
+}
+`
+	err = os.WriteFile(repoFile, []byte(repoContents), 0644)
+	require.NoError(t, err)
+
+	// and ensure we have testdistro-1 now
+	registry, err = newRepoRegistryImpl(dataDir, nil)
+	require.NoError(t, err)
+	repos, err := registry.DistroHasRepos("testdistro-1", "x86_64")
+	require.NoError(t, err)
+	assert.Len(t, repos, 1)
+	assert.Equal(t, repos[0].Name, "testdistro-1-repo")
+}