diff --git a/node-gcm/node-gcm.d.ts b/node-gcm/node-gcm.d.ts
index 3272acac4..cac54f31a 100644
--- a/node-gcm/node-gcm.d.ts
+++ b/node-gcm/node-gcm.d.ts
@@ -10,6 +10,9 @@ declare module "node-gcm" {
         delayWhileIdle?: boolean;
         timeToLive?: number;
         dryRun?: boolean;
+        data: {
+            [key: string]: string;
+        };
     }
 
     export class Message {
@@ -20,7 +23,7 @@ declare module "node-gcm" {
         dryRun: boolean;
 
         addData(key: string, value: string): void;
-        addData(data: any): void;
+        addData(data: { [key: string]: string }): void;
     }