diff --git a/gulp-size/gulp-size.d.ts b/gulp-size/gulp-size.d.ts
index 022e9b171..ba13c55a2 100644
--- a/gulp-size/gulp-size.d.ts
+++ b/gulp-size/gulp-size.d.ts
@@ -6,20 +6,20 @@
 /// <reference path="../node/node.d.ts" />
 
 declare module 'gulp-size' {
-    interface IOptions {
-        showFiles?: boolean;
-        gzip?: boolean;
-        title?: string;
+    namespace size {
+        interface Options {
+            showFiles?: boolean;
+            gzip?: boolean;
+            title?: string;
+        }
+
+        interface SizeStream extends NodeJS.ReadWriteStream {
+            size: number;
+            prettySize: string;
+        }
     }
 
-    interface ISizeStream extends NodeJS.ReadWriteStream {
-      size: number;
-      prettySize: string;
-    }
-
-    function size(options?: IOptions): ISizeStream;
-
-    namespace size {}
+    function size(options?: size.Options): size.SizeStream;
 
     export = size;
 }