diff --git a/types/sprintf/index.d.ts b/types/sprintf/index.d.ts
index 018a1a33b1..f9c3396e6a 100644
--- a/types/sprintf/index.d.ts
+++ b/types/sprintf/index.d.ts
@@ -1,10 +1,10 @@
-// Type definitions for sprintff
-// Project: https://github.com/maritz/node-sprintff
+// Type definitions for sprintf 0.1
+// Project: https://github.com/maritz/node-sprintf
 // Definitions by: Carlos Ballesteros Velasco <https://github.com/soywiz>
+//                 BendingBender <https://github.com/BendingBender>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
 // Imported from: https://github.com/soywiz/typescript-node-definitions/sprintff.d.ts
 
-
-export declare function sprintf(fmt: string, ...args: any[]): string;
-export declare function vsprintf(fmt: string, args: any[]): string;
+export function sprintf(fmt: string, ...args: any[]): string;
+export function vsprintf(fmt: string, args: any[]): string;
diff --git a/types/sprintf/sprintf-tests.ts b/types/sprintf/sprintf-tests.ts
index 3dca1f4f02..0ad5f0b937 100644
--- a/types/sprintf/sprintf-tests.ts
+++ b/types/sprintf/sprintf-tests.ts
@@ -1,13 +1,12 @@
-
 import sprintf = require('sprintf');
 
-var str: string;
-var num: number;
+declare const str: string;
+declare const num: number;
 
-sprintf.sprintf(str, str);
+sprintf.sprintf(str, str); // $ExpectType string
 sprintf.sprintf(str, str, num);
 sprintf.sprintf(str, num, str);
 
-sprintf.vsprintf(str, [str]);
+sprintf.vsprintf(str, [str]); // $ExpectType string
 sprintf.vsprintf(str, [str, num]);
 sprintf.vsprintf(str, [num, str]);
diff --git a/types/sprintf/tsconfig.json b/types/sprintf/tsconfig.json
index c71ae46eb4..e8d46d5357 100644
--- a/types/sprintf/tsconfig.json
+++ b/types/sprintf/tsconfig.json
@@ -6,7 +6,7 @@
         ],
         "noImplicitAny": true,
         "noImplicitThis": true,
-        "strictNullChecks": false,
+        "strictNullChecks": true,
         "baseUrl": "../",
         "typeRoots": [
             "../"
@@ -19,4 +19,4 @@
         "index.d.ts",
         "sprintf-tests.ts"
     ]
-}
\ No newline at end of file
+}
diff --git a/types/sprintf/tslint.json b/types/sprintf/tslint.json
new file mode 100644
index 0000000000..3db14f85ea
--- /dev/null
+++ b/types/sprintf/tslint.json
@@ -0,0 +1 @@
+{ "extends": "dtslint/dt.json" }