diff --git a/x-pack/legacy/plugins/siem/server/plugin.ts b/x-pack/legacy/plugins/siem/server/plugin.ts
index 3221adbf12539..e15248e5200ee 100644
--- a/x-pack/legacy/plugins/siem/server/plugin.ts
+++ b/x-pack/legacy/plugins/siem/server/plugin.ts
@@ -37,7 +37,7 @@ export interface SetupPlugins {
   encryptedSavedObjects: EncryptedSavedObjectsSetup;
   features: FeaturesSetup;
   security: SecuritySetup;
-  spaces: SpacesSetup;
+  spaces?: SpacesSetup;
 }
 
 export interface StartPlugins {
diff --git a/x-pack/legacy/plugins/siem/server/services/clients.test.ts b/x-pack/legacy/plugins/siem/server/services/clients.test.ts
new file mode 100644
index 0000000000000..7f63a8f5e949c
--- /dev/null
+++ b/x-pack/legacy/plugins/siem/server/services/clients.test.ts
@@ -0,0 +1,32 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import { coreMock, httpServerMock } from '../../../../../../src/core/server/mocks';
+import { actionsMock } from '../../../../../plugins/actions/server/mocks';
+
+import { ClientsService } from './clients';
+
+describe('ClientsService', () => {
+  describe('spacesClient', () => {
+    describe('#getSpaceId', () => {
+      it('returns the default spaceId if spaces are disabled', async () => {
+        const clients = new ClientsService();
+
+        const actions = actionsMock.createStart();
+        const { elasticsearch } = coreMock.createSetup();
+        const { savedObjects } = coreMock.createStart();
+        const request = httpServerMock.createRawRequest();
+        const spacesService = undefined;
+
+        clients.setup(elasticsearch.dataClient, spacesService);
+        clients.start(savedObjects, actions);
+
+        const { spacesClient } = await clients.createGetScoped()(request);
+        expect(spacesClient.getSpaceId()).toEqual('default');
+      });
+    });
+  });
+});
diff --git a/x-pack/legacy/plugins/siem/server/services/clients.ts b/x-pack/legacy/plugins/siem/server/services/clients.ts
index cb78f6e5c7838..ca50eda4e7a6c 100644
--- a/x-pack/legacy/plugins/siem/server/services/clients.ts
+++ b/x-pack/legacy/plugins/siem/server/services/clients.ts
@@ -13,7 +13,8 @@ import {
 } from '../../../../../../src/core/server';
 import { ActionsClient } from '../../../../../plugins/actions/server';
 import { AlertsClient } from '../../../../../legacy/plugins/alerting/server';
-import { CoreStart, StartPlugins, SetupPlugins } from '../plugin';
+import { SpacesServiceSetup } from '../../../../../plugins/spaces/server';
+import { CoreStart, StartPlugins } from '../plugin';
 
 export interface Clients {
   actionsClient?: ActionsClient;
@@ -30,12 +31,9 @@ export class ClientsService {
   private actions?: StartPlugins['actions'];
   private clusterClient?: IClusterClient;
   private savedObjects?: CoreStart['savedObjects'];
-  private spacesService?: SetupPlugins['spaces']['spacesService'];
+  private spacesService?: SpacesServiceSetup;
 
-  public setup(
-    clusterClient: IClusterClient,
-    spacesService: SetupPlugins['spaces']['spacesService']
-  ) {
+  public setup(clusterClient: IClusterClient, spacesService?: SpacesServiceSetup) {
     this.clusterClient = clusterClient;
     this.spacesService = spacesService;
   }