diff --git a/node-gcm/node-gcm.d.ts b/node-gcm/node-gcm.d.ts
index 82b3d1957..8a467cfe8 100644
--- a/node-gcm/node-gcm.d.ts
+++ b/node-gcm/node-gcm.d.ts
@@ -24,7 +24,7 @@ declare module "node-gcm" {
         timeToLive?: number;
         restrictedPackageName?: string;
         dryRun?: boolean;
-        data: {
+        data?: {
             [key: string]: string;
         };
         notification?: INotificationOptions;