diff --git a/src/interface.ts b/src/interface.ts
index 8ea4ea7..8e15093 100644
--- a/src/interface.ts
+++ b/src/interface.ts
@@ -21,6 +21,8 @@ export type MaybeZodObjectArray<T extends EventArgs> =
 export interface IDiscordSDK {
   readonly clientId: string;
   readonly instanceId: string;
+  readonly customId: string | null;
+  readonly referrerId: string | null;
   readonly platform: Platform;
   readonly mobileAppVersion: string | null;
   readonly sdkVersion: string;
diff --git a/src/mock.ts b/src/mock.ts
index 03f6329..8a589f3 100644
--- a/src/mock.ts
+++ b/src/mock.ts
@@ -13,6 +13,8 @@ export class DiscordSDKMock implements IDiscordSDK {
   readonly clientId: string;
   readonly platform = Platform.DESKTOP;
   readonly instanceId = '123456789012345678';
+  readonly customId: string | null;
+  readonly referrerId: string | null;
   readonly configuration = getDefaultSdkConfiguration();
   readonly source: Window | WindowProxy | null = null;
   readonly sourceOrigin: string = '';
@@ -33,6 +35,8 @@ export class DiscordSDKMock implements IDiscordSDK {
     this.guildId = guildId;
     this.channelId = channelId;
     this.locationId = locationId;
+    this.customId = null;
+    this.referrerId = null;
   }
 
   _updateCommandMocks(newCommands: Partial<IDiscordSDK['commands']>) {