diff --git a/package.json b/package.json
index 1e1575a..5e2c445 100644
--- a/package.json
+++ b/package.json
@@ -22,11 +22,9 @@
     "typescript": "tsc -p tsconfig.json"
   },
   "dependencies": {
-    "create-react-context": "^0.1.5",
-    "tickedoff": "^1.0.1"
+    "create-react-context": "^0.1.5"
   },
   "peerDependencies": {
-    "prop-types": "^15.5.0",
     "react": "^15.0.0 || ^16.0.0"
   },
   "devDependencies": {
diff --git a/src/unstated.d.ts b/src/unstated.d.ts
index 17ea382..01ea00c 100644
--- a/src/unstated.d.ts
+++ b/src/unstated.d.ts
@@ -3,11 +3,13 @@ import * as React from 'react';
 export class Container<State extends object> {
   state: State;
   setState<K extends keyof State>(
-    state: ((prevState: Readonly<State>) => (Partial<State> | State | null)) | (Partial<State> | State | null),
+    state:
+      | ((prevState: Readonly<State>) => Partial<State> | State | null)
+      | (Partial<State> | State | null),
     callback?: () => void
-  ): void;
-  subscribe(fn: Function): void;
-  unsubscribe(fn: Function): void;
+  ): Promise<void>;
+  subscribe(fn: () => any): void;
+  unsubscribe(fn: () => any): void;
 }
 
 export interface ContainerType<State extends object> {
diff --git a/src/unstated.js b/src/unstated.js
index c8a5778..199bd78 100644
--- a/src/unstated.js
+++ b/src/unstated.js
@@ -1,10 +1,8 @@
 // @flow
 import React, { type Node } from 'react';
 import createReactContext from 'create-react-context';
-import PropTypes from 'prop-types';
-import defer from 'tickedoff';
 
-type Listener = (cb?: () => void) => void;
+type Listener = () => mixed;
 
 const StateContext = createReactContext(null);
 
@@ -19,8 +17,8 @@ export class Container<State: {}> {
   setState(
     updater: $Shape<State> | ((prevState: $Shape<State>) => $Shape<State>),
     callback?: () => void
-  ) {
-    defer(() => {
+  ): Promise<void> {
+    return Promise.resolve().then(() => {
       let nextState;
 
       if (typeof updater === 'function') {
@@ -36,23 +34,12 @@ export class Container<State: {}> {
 
       this.state = Object.assign({}, this.state, nextState);
 
-      let completed = 0;
-      let total = this._listeners.length;
+      let promises = this._listeners.map(listener => listener());
 
-      this._listeners.forEach(fn => {
-        if (!callback) {
-          fn();
-          return;
+      return Promise.all(promises).then(() => {
+        if (callback) {
+          return callback();
         }
-
-        let safeCallback = callback;
-
-        fn(() => {
-          completed++;
-          if (completed < total) {
-            safeCallback();
-          }
-        });
       });
     });
   }
@@ -85,11 +72,6 @@ export class Subscribe<Containers: ContainersType> extends React.Component<
   SubscribeProps<Containers>,
   SubscribeState
 > {
-  static propTypes = {
-    to: PropTypes.array.isRequired,
-    children: PropTypes.func.isRequired
-  };
-
   state = {};
   instances: Array<ContainerType> = [];
 
@@ -103,8 +85,10 @@ export class Subscribe<Containers: ContainersType> extends React.Component<
     });
   }
 
-  onUpdate: Listener = cb => {
-    this.setState(DUMMY_STATE, cb);
+  onUpdate: Listener = () => {
+    return new Promise(resolve => {
+      this.setState(DUMMY_STATE, resolve);
+    });
   };
 
   _createInstances(