diff --git a/internal/repo/store.go b/internal/repo/store.go
index 3b8a263..d24d910 100644
--- a/internal/repo/store.go
+++ b/internal/repo/store.go
@@ -78,6 +78,9 @@ func (s *Store) UpdateRepoSetupStatus(ctx context.Context, id RepoID, status str
 	if err != nil {
 		return err
 	}
+	if current.SetupStatus == status {
+		return nil
+	}
 	if !isValidTransition(current.SetupStatus, status) {
 		return fmt.Errorf("invalid setup status transition from %q to %q", current.SetupStatus, status)
 	}
diff --git a/internal/repoapi/http_handler_test.go b/internal/repoapi/http_handler_test.go
index 69672a5..7bfda71 100644
--- a/internal/repoapi/http_handler_test.go
+++ b/internal/repoapi/http_handler_test.go
@@ -146,6 +146,28 @@ func TestUpdateSetup_MarkReady(t *testing.T) {
 	assert.NotNil(t, res.Data.SetupCompletedAt, "setup_completed_at should be set")
 }
 
+func TestUpdateSetup_MarkReadyWhenAlreadyReady(t *testing.T) {
+	f := newFixture(t)
+	r := f.addRepo("owner/test-repo")
+
+	// Move repo to ready (pending → scanning → ready)
+	ctx := context.Background()
+	require.NoError(t, f.RepoStore.UpdateRepoSetupStatus(ctx, r.ID, repo.SetupStatusScanning))
+	require.NoError(t, f.RepoStore.UpdateRepoSetupStatus(ctx, r.ID, repo.SetupStatusReady))
+
+	// Editing expectations from settings dialog when repo is already ready
+	// should not fail with internal server error.
+	expectations := "## Updated expectations"
+	req := repoapi.UpdateSetupRequest{
+		Expectations: &expectations,
+		MarkReady:    true,
+	}
+	res := doPatch[server.Response[repo.Repo]](t, f.repoSetupURL(r.ID), req)
+	assert.Equal(t, "## Updated expectations", res.Data.Expectations)
+	assert.Equal(t, repo.SetupStatusReady, res.Data.SetupStatus, "should remain ready")
+	assert.NotNil(t, res.Data.SetupCompletedAt, "setup_completed_at should be set")
+}
+
 func TestUpdateSetup_Combined(t *testing.T) {
 	f := newFixture(t)
 	r := f.addRepo("owner/test-repo")