diff --git a/clientapi/routing/key_crosssigning.go b/clientapi/routing/key_crosssigning.go
index bbc75416..50c4736a 100644
--- a/clientapi/routing/key_crosssigning.go
+++ b/clientapi/routing/key_crosssigning.go
@@ -25,6 +25,8 @@ import (
 )
 
 func UploadCrossSigningDeviceKeys(req *http.Request, keyserverAPI api.KeyInternalAPI, device *userapi.Device) util.JSONResponse {
+	// TODO: User-interactive auth
+
 	uploadReq := &api.PerformUploadDeviceKeysRequest{}
 	uploadRes := &api.PerformUploadDeviceKeysResponse{}
 
diff --git a/clientapi/routing/routing.go b/clientapi/routing/routing.go
index 3584fbab..3e36b292 100644
--- a/clientapi/routing/routing.go
+++ b/clientapi/routing/routing.go
@@ -64,7 +64,9 @@ func Setup(
 	rateLimits := newRateLimits(&cfg.RateLimiting)
 	userInteractiveAuth := auth.NewUserInteractive(accountDB.GetAccountByPassword, cfg)
 
-	unstableFeatures := make(map[string]bool)
+	unstableFeatures := map[string]bool{
+		"org.matrix.e2e_cross_signing": true,
+	}
 	for _, msc := range cfg.MSCs.MSCs {
 		unstableFeatures["org.matrix."+msc] = true
 	}
diff --git a/syncapi/internal/keychange_test.go b/syncapi/internal/keychange_test.go
index 44c4a4dd..38be34f6 100644
--- a/syncapi/internal/keychange_test.go
+++ b/syncapi/internal/keychange_test.go
@@ -33,6 +33,10 @@ func (k *mockKeyAPI) SetUserAPI(i userapi.UserInternalAPI) {}
 // PerformClaimKeys claims one-time keys for use in pre-key messages
 func (k *mockKeyAPI) PerformClaimKeys(ctx context.Context, req *keyapi.PerformClaimKeysRequest, res *keyapi.PerformClaimKeysResponse) {
 }
+func (k *mockKeyAPI) PerformUploadDeviceKeys(ctx context.Context, req *keyapi.PerformUploadDeviceKeysRequest, res *keyapi.PerformUploadDeviceKeysResponse) {
+}
+func (k *mockKeyAPI) PerformUploadDeviceSignatures(ctx context.Context, req *keyapi.PerformUploadDeviceSignaturesRequest, res *keyapi.PerformUploadDeviceSignaturesResponse) {
+}
 func (k *mockKeyAPI) QueryKeys(ctx context.Context, req *keyapi.QueryKeysRequest, res *keyapi.QueryKeysResponse) {
 }
 func (k *mockKeyAPI) QueryKeyChanges(ctx context.Context, req *keyapi.QueryKeyChangesRequest, res *keyapi.QueryKeyChangesResponse) {