diff --git a/types/zen-observable/esm.d.ts b/types/zen-observable/esm.d.ts
new file mode 100644
index 0000000000..786e2e639d
--- /dev/null
+++ b/types/zen-observable/esm.d.ts
@@ -0,0 +1,14 @@
+import Observable = require('.');
+
+/**
+ * @see https://github.com/zenparsing/zen-observable/blob/master/esm.js
+ */
+export default Observable;
+export { Observable };
+export * from './extras';
+
+export type SubscriptionObserver<T> = ZenObservable.SubscriptionObserver<T>;
+export type Subscription = ZenObservable.Subscription;
+export type Observer<T> = ZenObservable.Observer<T>;
+export type Subscriber<T> = ZenObservable.Subscriber<T>;
+export type ObservableLike<T> = ZenObservable.ObservableLike<T>;
diff --git a/types/zen-observable/extras.d.ts b/types/zen-observable/extras.d.ts
new file mode 100644
index 0000000000..ccacdda7f4
--- /dev/null
+++ b/types/zen-observable/extras.d.ts
@@ -0,0 +1,97 @@
+import Observable = require('.');
+
+export function merge(): Observable<never>;
+export function merge<A>(a: ZenObservable.ObservableLike<A>): Observable<A>;
+export function merge<A, B>(a: ZenObservable.ObservableLike<A>, b: ZenObservable.ObservableLike<B>): Observable<A | B>;
+export function merge<A, B, C>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+    c: ZenObservable.ObservableLike<C>,
+): Observable<A | B | C>;
+export function merge<A, B, C, D>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+    c: ZenObservable.ObservableLike<C>,
+    d: ZenObservable.ObservableLike<D>,
+): Observable<A | B | C | D>;
+export function merge<A, B, C, D, E>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+    c: ZenObservable.ObservableLike<C>,
+    d: ZenObservable.ObservableLike<D>,
+    e: ZenObservable.ObservableLike<E>,
+): Observable<A | B | C | D | E>;
+export function merge<A, B, C, D, E, F>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+    c: ZenObservable.ObservableLike<C>,
+    d: ZenObservable.ObservableLike<D>,
+    e: ZenObservable.ObservableLike<E>,
+    f: ZenObservable.ObservableLike<F>,
+): Observable<A | B | C | D | E | F>;
+export function merge<T>(...observables: Array<ZenObservable.ObservableLike<T>>): Observable<T>;
+
+export function combineLatest(): Observable<never>;
+export function combineLatest<A>(a: ZenObservable.ObservableLike<A>): Observable<[A]>;
+export function combineLatest<A, B>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+): Observable<[A, B]>;
+export function combineLatest<A, B, C>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+    c: ZenObservable.ObservableLike<C>,
+): Observable<[A, B, C]>;
+export function combineLatest<A, B, C, D>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+    c: ZenObservable.ObservableLike<C>,
+    d: ZenObservable.ObservableLike<D>,
+): Observable<[A, B, C, D]>;
+export function combineLatest<A, B, C, D, E>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+    c: ZenObservable.ObservableLike<C>,
+    d: ZenObservable.ObservableLike<D>,
+    e: ZenObservable.ObservableLike<E>,
+): Observable<[A, B, C, D, E]>;
+export function combineLatest<A, B, C, D, E, F>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+    c: ZenObservable.ObservableLike<C>,
+    d: ZenObservable.ObservableLike<D>,
+    e: ZenObservable.ObservableLike<E>,
+    f: ZenObservable.ObservableLike<F>,
+): Observable<[A, B, C, D, E, F]>;
+export function combineLatest<T>(...observables: Array<ZenObservable.ObservableLike<T>>): Observable<T[]>;
+
+export function zip(): Observable<never>;
+export function zip<A>(a: ZenObservable.ObservableLike<A>): Observable<[A]>;
+export function zip<A, B>(a: ZenObservable.ObservableLike<A>, b: ZenObservable.ObservableLike<B>): Observable<[A, B]>;
+export function zip<A, B, C>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+    c: ZenObservable.ObservableLike<C>,
+): Observable<[A, B, C]>;
+export function zip<A, B, C, D>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+    c: ZenObservable.ObservableLike<C>,
+    d: ZenObservable.ObservableLike<D>,
+): Observable<[A, B, C, D]>;
+export function zip<A, B, C, D, E>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+    c: ZenObservable.ObservableLike<C>,
+    d: ZenObservable.ObservableLike<D>,
+    e: ZenObservable.ObservableLike<E>,
+): Observable<[A, B, C, D, E]>;
+export function zip<A, B, C, D, E, F>(
+    a: ZenObservable.ObservableLike<A>,
+    b: ZenObservable.ObservableLike<B>,
+    c: ZenObservable.ObservableLike<C>,
+    d: ZenObservable.ObservableLike<D>,
+    e: ZenObservable.ObservableLike<E>,
+    f: ZenObservable.ObservableLike<F>,
+): Observable<[A, B, C, D, E, F]>;
+export function zip<T>(...observables: Array<ZenObservable.ObservableLike<T>>): Observable<T[]>;
diff --git a/types/zen-observable/index.d.ts b/types/zen-observable/index.d.ts
index 94ca94ccd2..c242b92fc9 100644
--- a/types/zen-observable/index.d.ts
+++ b/types/zen-observable/index.d.ts
@@ -3,6 +3,7 @@
 // Definitions by: Kombu <https://github.com/aicest>
 //                 JounQin <https://github.com/JounQin>
 //                 Thomas <https://github.com/itomtom>
+//                 BenoitZugmeyer <https://github.com/BenoitZugmeyer>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
 declare global {
@@ -40,10 +41,14 @@ declare global {
 }
 
 declare class Observable<T> {
-    constructor(subscriber: ZenObservable.Subscriber<T>)
+    constructor(subscriber: ZenObservable.Subscriber<T>);
 
     subscribe(observer: ZenObservable.Observer<T>): ZenObservable.Subscription;
-    subscribe(onNext: (value: T) => void, onError?: (error: any) => void, onComplete?: () => void): ZenObservable.Subscription;
+    subscribe(
+        onNext: (value: T) => void,
+        onError?: (error: any) => void,
+        onComplete?: () => void,
+    ): ZenObservable.Subscription;
 
     [Symbol.observable](): Observable<T>;
 
@@ -59,7 +64,6 @@ declare class Observable<T> {
     static of<R>(...items: R[]): Observable<R>;
 }
 
-declare namespace Observable {
-}
+declare namespace Observable {}
 
 export = Observable;
diff --git a/types/zen-observable/test/esm.ts b/types/zen-observable/test/esm.ts
new file mode 100644
index 0000000000..a32eb4d8ec
--- /dev/null
+++ b/types/zen-observable/test/esm.ts
@@ -0,0 +1,83 @@
+import Observable, { Subscription, SubscriptionObserver, zip, combineLatest, merge } from 'zen-observable/esm';
+
+// $ExpectType Subscription
+let subscription = new Observable<number>(
+    (
+        // $ExpectType SubscriptionObserver<number>
+        observer,
+    ) => {
+        observer.next(1);
+        observer.complete();
+    },
+).subscribe(
+    (
+        // $ExpectType number
+        val,
+    ) => {},
+);
+
+// zip
+zip(Observable.of(1, 2, 3), Observable.of('a', 'b', 'c')).subscribe(
+    (
+        // $ExpectType [number, string]
+        val,
+    ) => {},
+);
+
+zip().subscribe(
+    (
+        // $ExpectType never
+        val,
+    ) => {},
+);
+
+zip(...[Observable.of(1)]).subscribe(
+    (
+        // $ExpectType number[]
+        val,
+    ) => {},
+);
+
+// merge
+merge(Observable.of(1, 2, 3), Observable.of('a', 'b', 'c')).subscribe(
+    (
+        // $ExpectType string | number
+        val,
+    ) => {},
+);
+
+merge().subscribe(
+    (
+        // $ExpectType never
+        val,
+    ) => {},
+);
+
+merge(...[Observable.of(1)]).subscribe(
+    (
+        // $ExpectType number
+        val,
+    ) => {},
+);
+
+// combineLatest
+combineLatest(Observable.of(1, 2, 3), Observable.of('a', 'b', 'c')).subscribe(
+    (
+        // $ExpectType [number, string]
+        val,
+    ) => {},
+);
+
+combineLatest().subscribe(
+    (
+        // $ExpectType never
+        val,
+    ) => {},
+);
+
+combineLatest(...[Observable.of(1)]).subscribe(
+    (
+        // $ExpectType number[]
+        val,
+    ) => {},
+);
diff --git a/types/zen-observable/zen-observable-tests.ts b/types/zen-observable/test/index.ts
similarity index 76%
rename from types/zen-observable/zen-observable-tests.ts
rename to types/zen-observable/test/index.ts
index b1aea6d46a..680306ea87 100644
--- a/types/zen-observable/zen-observable-tests.ts
+++ b/types/zen-observable/test/index.ts
@@ -13,25 +13,21 @@ function assert(val: boolean) {
 new Observable<number>(observer => {
     [1, 2, 3].forEach(one => observer.next(one));
     observer.complete();
-})
-    .subscribe(val => assert(typeof val === 'number'));
+}).subscribe(val => assert(typeof val === 'number'));
 
 /**
  * Observable.of
  */
 
-Observable.of(1, 2, 3)
-    .subscribe(val => assert(typeof val === 'number'));
+Observable.of(1, 2, 3).subscribe(val => assert(typeof val === 'number'));
 
 /**
  * Observable.from
  */
 
-Observable.from(Observable.of(1, 2, 3))
-    .subscribe(val => assert(typeof val === 'number'));
+Observable.from(Observable.of(1, 2, 3)).subscribe(val => assert(typeof val === 'number'));
 
-Observable.from([1, 2, 3])
-    .subscribe(val => assert(typeof val === 'number'));
+Observable.from([1, 2, 3]).subscribe(val => assert(typeof val === 'number'));
 
 Observable.from({
     subscribe(observer: ZenObservable.SubscriptionObserver<number>) {
@@ -40,23 +36,20 @@ Observable.from({
     },
     [Symbol.observable](this: ZenObservable.ObservableLike<number>) {
         return this;
-    }
-})
-    .subscribe(val => assert(typeof val === 'number'));
+    },
+}).subscribe(val => assert(typeof val === 'number'));
 
 Observable.from({
     [Symbol.observable]() {
         return Observable.of(1, 2, 3);
-    }
-})
-    .subscribe(val => assert(typeof val === 'number'));
+    },
+}).subscribe(val => assert(typeof val === 'number'));
 
 /**
  * observable.forEach
  */
 
-Observable.of(1, 2, 3)
-    .forEach(val => assert(typeof val === 'number'));
+Observable.of(1, 2, 3).forEach(val => assert(typeof val === 'number'));
 
 /**
  * observable.map
@@ -99,8 +92,8 @@ Observable.of(1, 2, 3)
  */
 
 Observable.of(1, 2, 3)
-.concat(Observable.of(4, 5, 6), Observable.of(7, 8, 9))
-.subscribe(val => assert(typeof val === 'number'));
+    .concat(Observable.of(4, 5, 6), Observable.of(7, 8, 9))
+    .subscribe(val => assert(typeof val === 'number'));
 
 /**
  * ZenObservable
diff --git a/types/zen-observable/tsconfig.json b/types/zen-observable/tsconfig.json
index d3daca16e3..b5026e2b77 100644
--- a/types/zen-observable/tsconfig.json
+++ b/types/zen-observable/tsconfig.json
@@ -18,6 +18,7 @@
     },
     "files": [
         "index.d.ts",
-        "zen-observable-tests.ts"
+        "test/index.ts",
+        "test/esm.ts"
     ]
 }