diff --git a/zip.js/zip.js-tests.ts b/zip.js/zip.js-tests.ts
index fa085ca38a..b006549960 100644
--- a/zip.js/zip.js-tests.ts
+++ b/zip.js/zip.js-tests.ts
@@ -1,3 +1,5 @@
+/// <reference path="zip.js.d.ts" />
+
 // create the blob object storing the data to compress
 var blob: Blob = new Blob([ "Lorem ipsum dolor sit amet, consectetuer adipiscing elit..." ], {
   type : "text/plain"
@@ -38,6 +40,6 @@ function unzipBlob(blob: Blob, callback: (unzippedBlob: Blob) => void) {
   }, theErrorHandler);
 }
 
-function theErrorHandler(message) {
+function theErrorHandler(message: any) {
   console.error(message);
 }
\ No newline at end of file
diff --git a/zip.js/zip.js.d.ts b/zip.js/zip.js.d.ts
index 3c026cd7ac..fa976dca9b 100644
--- a/zip.js/zip.js.d.ts
+++ b/zip.js/zip.js.d.ts
@@ -58,7 +58,7 @@ declare module zip {
 	export class Writer {
 		public init(callback: () => void, onerror?: (error: any) => void): void;
 		public writeUint8Array(array: Uint8Array, callback: () => void, onerror?: (error: any) => void): void;
-		public getData(callback: (data) => void, onerror?: (error: any) => void) : void;
+		public getData(callback: (data: any) => void, onerror?: (error: any) => void) : void;
 	}
 
 	export class TextWriter extends Writer {