diff --git a/types/node/index.d.ts b/types/node/index.d.ts
index 52186217bd..72071c7c56 100644
--- a/types/node/index.d.ts
+++ b/types/node/index.d.ts
@@ -1278,21 +1278,21 @@ declare module "zlib" {
     export function deflateRaw(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
     export function deflateRaw(buf: Buffer | string, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
     export function deflateRawSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
-    export function gzip(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function gzip(buf: Buffer, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
-    export function gzipSync(buf: Buffer, options?: ZlibOptions): Buffer;
-    export function gunzip(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function gunzip(buf: Buffer, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
-    export function gunzipSync(buf: Buffer, options?: ZlibOptions): Buffer;
-    export function inflate(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function inflate(buf: Buffer, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
-    export function inflateSync(buf: Buffer, options?: ZlibOptions): Buffer;
-    export function inflateRaw(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function inflateRaw(buf: Buffer, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
-    export function inflateRawSync(buf: Buffer, options?: ZlibOptions): Buffer;
-    export function unzip(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function unzip(buf: Buffer, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
-    export function unzipSync(buf: Buffer, options?: ZlibOptions): Buffer;
+    export function gzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function gzip(buf: Buffer | string, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
+    export function gzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function gunzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function gunzip(buf: Buffer | string, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
+    export function gunzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function inflate(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function inflate(buf: Buffer | string, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
+    export function inflateSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function inflateRaw(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function inflateRaw(buf: Buffer | string, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
+    export function inflateRawSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function unzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function unzip(buf: Buffer | string, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
+    export function unzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
 
     export namespace constants {
         // Allowed flush values.
diff --git a/types/node/node-tests.ts b/types/node/node-tests.ts
index ecd315eee9..7fab05644f 100644
--- a/types/node/node-tests.ts
+++ b/types/node/node-tests.ts
@@ -2820,3 +2820,19 @@ namespace async_hooks_tests {
     const tId: number = async_hooks.triggerAsyncId();
     const eId: number = async_hooks.executionAsyncId();
 }
+
+////////////////////////////////////////////////////
+/// zlib tests : http://nodejs.org/api/zlib.html ///
+////////////////////////////////////////////////////
+
+namespace zlib_tests {
+    {
+        const gzipped = zlib.gzipSync('test');
+        const unzipped = zlib.gunzipSync(gzipped.toString());
+    }
+
+    {
+        const deflate = zlib.deflateSync('test');
+        const inflate = zlib.inflateSync(deflate.toString());
+    }
+}
diff --git a/types/node/v0/index.d.ts b/types/node/v0/index.d.ts
index fdbf9dd518..aa7996021c 100644
--- a/types/node/v0/index.d.ts
+++ b/types/node/v0/index.d.ts
@@ -664,20 +664,20 @@ declare module "zlib" {
     export function createInflateRaw(options?: ZlibOptions): InflateRaw;
     export function createUnzip(options?: ZlibOptions): Unzip;
 
-    export function deflate(buf: Buffer, callback: (error: Error, result: any) =>void ): void;
-    export function deflateSync(buf: Buffer, options?: ZlibOptions): any;
-    export function deflateRaw(buf: Buffer, callback: (error: Error, result: any) =>void ): void;
-    export function deflateRawSync(buf: Buffer, options?: ZlibOptions): any;
-    export function gzip(buf: Buffer, callback: (error: Error, result: any) =>void ): void;
-    export function gzipSync(buf: Buffer, options?: ZlibOptions): any;
-    export function gunzip(buf: Buffer, callback: (error: Error, result: any) =>void ): void;
-    export function gunzipSync(buf: Buffer, options?: ZlibOptions): any;
-    export function inflate(buf: Buffer, callback: (error: Error, result: any) =>void ): void;
-    export function inflateSync(buf: Buffer, options?: ZlibOptions): any;
-    export function inflateRaw(buf: Buffer, callback: (error: Error, result: any) =>void ): void;
-    export function inflateRawSync(buf: Buffer, options?: ZlibOptions): any;
-    export function unzip(buf: Buffer, callback: (error: Error, result: any) =>void ): void;
-    export function unzipSync(buf: Buffer, options?: ZlibOptions): any;
+    export function deflate(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function deflateSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function deflateRaw(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function deflateRawSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function gzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function gzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function gunzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function gunzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function inflate(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function inflateSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function inflateRaw(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function inflateRawSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function unzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function unzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
 
     // Constants
     export var Z_NO_FLUSH: number;
diff --git a/types/node/v0/node-tests.ts b/types/node/v0/node-tests.ts
index 6c94757bf7..91e85f5a0c 100644
--- a/types/node/v0/node-tests.ts
+++ b/types/node/v0/node-tests.ts
@@ -448,3 +448,19 @@ namespace string_decoder_tests {
 
 childProcess.exec("echo test");
 childProcess.spawnSync("echo test");
+
+////////////////////////////////////////////////////
+/// zlib tests : http://nodejs.org/api/zlib.html ///
+////////////////////////////////////////////////////
+
+namespace zlib_tests {
+    {
+        const gzipped = zlib.gzipSync('test');
+        const unzipped = zlib.gunzipSync(gzipped.toString());
+    }
+
+    {
+        const deflate = zlib.deflateSync('test');
+        const inflate = zlib.inflateSync(deflate.toString());
+    }
+}
diff --git a/types/node/v4/index.d.ts b/types/node/v4/index.d.ts
index ad9f022b84..5e7bfd2926 100644
--- a/types/node/v4/index.d.ts
+++ b/types/node/v4/index.d.ts
@@ -802,20 +802,20 @@ declare module "zlib" {
     export function createInflateRaw(options?: ZlibOptions): InflateRaw;
     export function createUnzip(options?: ZlibOptions): Unzip;
 
-    export function deflate(buf: Buffer | string, callback: (error: Error, result: any) =>void ): void;
-    export function deflateSync(buf: Buffer | string, options?: ZlibOptions): any;
-    export function deflateRaw(buf: Buffer | string, callback: (error: Error, result: any) =>void ): void;
-    export function deflateRawSync(buf: Buffer | string, options?: ZlibOptions): any;
-    export function gzip(buf: Buffer | string, callback: (error: Error, result: any) =>void ): void;
-    export function gzipSync(buf: Buffer | string, options?: ZlibOptions): any;
-    export function gunzip(buf: Buffer | string, callback: (error: Error, result: any) =>void ): void;
-    export function gunzipSync(buf: Buffer | string, options?: ZlibOptions): any;
-    export function inflate(buf: Buffer | string, callback: (error: Error, result: any) =>void ): void;
-    export function inflateSync(buf: Buffer | string, options?: ZlibOptions): any;
-    export function inflateRaw(buf: Buffer | string, callback: (error: Error, result: any) =>void ): void;
-    export function inflateRawSync(buf: Buffer | string, options?: ZlibOptions): any;
-    export function unzip(buf: Buffer | string, callback: (error: Error, result: any) =>void ): void;
-    export function unzipSync(buf: Buffer | string, options?: ZlibOptions): any;
+    export function deflate(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function deflateSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function deflateRaw(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function deflateRawSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function gzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function gzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function gunzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function gunzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function inflate(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function inflateSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function inflateRaw(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function inflateRawSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function unzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function unzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
 
     // Constants
     export var Z_NO_FLUSH: number;
diff --git a/types/node/v6/index.d.ts b/types/node/v6/index.d.ts
index cbf93b8361..38b6d41798 100644
--- a/types/node/v6/index.d.ts
+++ b/types/node/v6/index.d.ts
@@ -1092,16 +1092,16 @@ declare module "zlib" {
     export function deflateSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
     export function deflateRaw(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
     export function deflateRawSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
-    export function gzip(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function gzipSync(buf: Buffer, options?: ZlibOptions): Buffer;
-    export function gunzip(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function gunzipSync(buf: Buffer, options?: ZlibOptions): Buffer;
-    export function inflate(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function inflateSync(buf: Buffer, options?: ZlibOptions): Buffer;
-    export function inflateRaw(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function inflateRawSync(buf: Buffer, options?: ZlibOptions): Buffer;
-    export function unzip(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function unzipSync(buf: Buffer, options?: ZlibOptions): Buffer;
+    export function gzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function gzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function gunzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function gunzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function inflate(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function inflateSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function inflateRaw(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function inflateRawSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function unzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function unzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
 
     // Constants
     export var Z_NO_FLUSH: number;
diff --git a/types/node/v6/node-tests.ts b/types/node/v6/node-tests.ts
index 6e5901541e..3607a5bec2 100644
--- a/types/node/v6/node-tests.ts
+++ b/types/node/v6/node-tests.ts
@@ -2366,3 +2366,19 @@ client.connect(8888, 'localhost');
 client.listbreakpoints((err, body, packet) => {
 
 });
+
+////////////////////////////////////////////////////
+/// zlib tests : http://nodejs.org/api/zlib.html ///
+////////////////////////////////////////////////////
+
+namespace zlib_tests {
+    {
+        const gzipped = zlib.gzipSync('test');
+        const unzipped = zlib.gunzipSync(gzipped.toString());
+    }
+
+    {
+        const deflate = zlib.deflateSync('test');
+        const inflate = zlib.inflateSync(deflate.toString());
+    }
+}
diff --git a/types/node/v7/index.d.ts b/types/node/v7/index.d.ts
index ffc19c34b1..4f40de2d58 100644
--- a/types/node/v7/index.d.ts
+++ b/types/node/v7/index.d.ts
@@ -1123,21 +1123,21 @@ declare module "zlib" {
     export function deflateRaw(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
     export function deflateRaw(buf: Buffer | string, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
     export function deflateRawSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
-    export function gzip(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function gzip(buf: Buffer, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
-    export function gzipSync(buf: Buffer, options?: ZlibOptions): Buffer;
-    export function gunzip(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function gunzip(buf: Buffer, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
-    export function gunzipSync(buf: Buffer, options?: ZlibOptions): Buffer;
-    export function inflate(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function inflate(buf: Buffer, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
-    export function inflateSync(buf: Buffer, options?: ZlibOptions): Buffer;
-    export function inflateRaw(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function inflateRaw(buf: Buffer, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
-    export function inflateRawSync(buf: Buffer, options?: ZlibOptions): Buffer;
-    export function unzip(buf: Buffer, callback: (error: Error, result: Buffer) => void): void;
-    export function unzip(buf: Buffer, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
-    export function unzipSync(buf: Buffer, options?: ZlibOptions): Buffer;
+    export function gzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function gzip(buf: Buffer | string, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
+    export function gzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function gunzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function gunzip(buf: Buffer | string, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
+    export function gunzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function inflate(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function inflate(buf: Buffer | string, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
+    export function inflateSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function inflateRaw(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function inflateRaw(buf: Buffer | string, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
+    export function inflateRawSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
+    export function unzip(buf: Buffer | string, callback: (error: Error, result: Buffer) => void): void;
+    export function unzip(buf: Buffer | string, options: ZlibOptions, callback: (error: Error, result: Buffer) => void): void;
+    export function unzipSync(buf: Buffer | string, options?: ZlibOptions): Buffer;
 
     export namespace constants {
         // Allowed flush values.
diff --git a/types/node/v7/node-tests.ts b/types/node/v7/node-tests.ts
index 60118e5eac..860a4dc56b 100644
--- a/types/node/v7/node-tests.ts
+++ b/types/node/v7/node-tests.ts
@@ -2510,3 +2510,19 @@ client.connect(8888, 'localhost');
 client.listbreakpoints((err, body, packet) => {
 
 });
+
+////////////////////////////////////////////////////
+/// zlib tests : http://nodejs.org/api/zlib.html ///
+////////////////////////////////////////////////////
+
+namespace zlib_tests {
+    {
+        const gzipped = zlib.gzipSync('test');
+        const unzipped = zlib.gunzipSync(gzipped.toString());
+    }
+
+    {
+        const deflate = zlib.deflateSync('test');
+        const inflate = zlib.inflateSync(deflate.toString());
+    }
+}