diff --git a/types/gulp-inject/gulp-inject-tests.ts b/types/gulp-inject/gulp-inject-tests.ts
index 4cba6ccc4a..ef29ebc343 100644
--- a/types/gulp-inject/gulp-inject-tests.ts
+++ b/types/gulp-inject/gulp-inject-tests.ts
@@ -39,3 +39,9 @@ gulp.task("inject:transform", () => {
         }))
         .pipe(gulp.dest("build"));
 });
+
+function createOptions(starttag: inject.ITagFunction): inject.IOptions {
+    return {
+        starttag: starttag
+    };
+}
diff --git a/types/gulp-inject/index.d.ts b/types/gulp-inject/index.d.ts
index a0c99efe78..ac6ec0172c 100644
--- a/types/gulp-inject/index.d.ts
+++ b/types/gulp-inject/index.d.ts
@@ -8,31 +8,31 @@
 
 import File = require("vinyl");
 
-interface ITagFunction {
-    (targetExt: string, sourceExt: string): string;
+declare function inject(sources: NodeJS.ReadableStream, options?: inject.IOptions): NodeJS.ReadWriteStream;
+
+declare namespace inject {
+    interface ITagFunction {
+        (targetExt: string, sourceExt: string): string;
+    }
+
+    interface ITransformFunction {
+        (filepath: string, file?: File, index?: number, length?: number, targetFile?: File): string;
+    }
+
+    interface IOptions {
+        ignorePath?: string | string[];
+        relative?: boolean;
+        addPrefix?: string;
+        addSuffix?: string;
+        addRootSlash?: boolean;
+        name?: string;
+        removeTags?: boolean;
+        empty?: boolean;
+        starttag?: string | ITagFunction;
+        endtag?: string | ITagFunction;
+        transform?: ITransformFunction;
+        selfClosingTag?: boolean;
+    }
 }
 
-interface ITransformFunction {
-    (filepath: string, file?: File, index?: number, length?: number, targetFile?: File): string;
-}
-
-interface IOptions {
-    ignorePath?: string | string[];
-    relative?: boolean;
-    addPrefix?: string;
-    addSuffix?: string;
-    addRootSlash?: boolean;
-    name?: string;
-    removeTags?: boolean;
-    empty?: boolean;
-    starttag?: string | ITagFunction;
-    endtag?: string | ITagFunction;
-    transform?: ITransformFunction;
-    selfClosingTag?: boolean;
-}
-
-declare function inject(sources: NodeJS.ReadableStream, options?: IOptions): NodeJS.ReadWriteStream;
-
-declare namespace inject { }
-
 export = inject;