diff --git a/doc/component.md b/doc/component.md
index a2c70bb7..a53fea97 100644
--- a/doc/component.md
+++ b/doc/component.md
@@ -146,11 +146,6 @@ find a template with the component name (or one of its ancestor).
   if we have a `isMobile` key in the environment, to decide if we want a mobile
   interface or a destkop one.
 
-- **`set(target, key, value)`**. This method is necessary in some cases when we
-  need to modify the state of the component in a way that is not visible to the
-  observer (see [observer's technical limitations](observer.md#technical-limitations)).
-  For example, if we need to add a key to the state.
-
 - **`destroy()`**. As its name suggests, this method will remove the component,
   and perform all necessary cleanup, such as unmounting the component, its children,
   removing the parent/children relationship. This method should almost never be
diff --git a/doc/observer.md b/doc/observer.md
index 35d50d45..48f61353 100644
--- a/doc/observer.md
+++ b/doc/observer.md
@@ -20,35 +20,31 @@ obj.a.b = 2;
 ## Technical Limitations
 
 Since the observer uses getters and setters, it is actually unable to react to
-changes in two situations:
+changes in three situations:
 
-- adding a key to an object:
+- adding a key to an object
+- deleting a key from an object
+- modifying an array by setting a new value at a given index
+
+In those situations, we need a way to tell the observer that something happened.
+This can be done by using the `set` and `delete` (only for objects) static
+methods of the `Observer`.
 
   ```javascript
   const observer = new owl.Observer();
   const obj = { a: 1 };
   observer.observe(obj);
-  obj.b = 2; // will do nothing
+  obj.b = 2; // won't notify the change
+  owl.Observer.set(obj, "b", 2); // will notify the change
+
+  delete obj.b; // won't notify the change
+  owl.Observer.delete(obj, "b"); // will notify the change
   ```
 
-  In that case, we need a way to tell the observer that something happened.
-  This can be done by using the `set` method:
-
-  ```javascript
-  observer.set(obj, "b", 2);
-  ```
-
-- modifying an array by setting a new value at a given index:
-
   ```javascript
   const observer = new owl.Observer();
-  const obj = { todos: [{ id: 1, text: "todo" }] };
-  observer.observe(obj);
-  obj[0] = { id: 2, text: "othertodo" }; // will do nothing, and obj[0] is not observed
-  ```
-
-  In that case, the solution is the same, we can simply use the `set` method:
-
-  ```javascript
-  observer.set(obj, 0, { id: 2, text: "othertodo" });
+  const arr = ["a"];
+  observer.observe(arr);
+  arr[0] = "b"; // won't notify the change
+  owl.Observer.set(arr, 0, "b"); // will notify the change
   ```
diff --git a/src/component.ts b/src/component.ts
index 4600d282..8c5614ad 100644
--- a/src/component.ts
+++ b/src/component.ts
@@ -340,14 +340,6 @@ export class Component<T extends Env, Props extends {}, State extends {}> {
     }
   }
 
-  /**
-   * Sets a key (from the state) to a specific value.  This is mostly useful to
-   * work around the limitation in observed value with new keys.
-   */
-  set(target: any, key: string | number, value: any) {
-    this.__owl__.observer!.set(target, key, value);
-  }
-
   /**
    * Emit a custom event of type 'eventType' with the given 'payload' on the
    * component's el, if it exists. However, note that the event will only bubble
diff --git a/src/observer.ts b/src/observer.ts
index efb1f67c..c5c665e2 100644
--- a/src/observer.ts
+++ b/src/observer.ts
@@ -76,6 +76,24 @@ export class Observer {
   allowMutations: boolean = true;
   dirty: boolean = false;
 
+  static set(target: any, key: number | string, value: any) {
+    if (!target.__owl__) {
+      throw Error(
+        "`Observer.set()` can only be called with observed Objects or Arrays"
+      );
+    }
+    target.__owl__.observer.set(target, key, value);
+  }
+
+  static delete(target: any, key: number | string) {
+    if (!target.__owl__) {
+      throw Error(
+        "`Observer.delete()` can only be called with observed Objects"
+      );
+    }
+    target.__owl__.observer.delete(target, key);
+  }
+
   notifyCB() {}
   notifyChange() {
     this.dirty = true;
@@ -120,8 +138,19 @@ export class Observer {
     this.notifyChange();
   }
 
+  delete(target: any, key: number | string) {
+    delete target[key];
+    this._updateRevNumber(target);
+    this.notifyChange();
+  }
+
   _observeObj<T extends { __owl__?: any }>(obj: T, parent?: any) {
-    obj.__owl__ = { rev: this.rev, deepRev: this.rev, parent };
+    obj.__owl__ = {
+      rev: this.rev,
+      deepRev: this.rev,
+      parent,
+      observer: this
+    };
     Object.defineProperty(obj, "__owl__", { enumerable: false });
     for (let key in obj) {
       this._addProp(obj, key, obj[key]);
@@ -129,7 +158,12 @@ export class Observer {
   }
 
   _observeArr(arr: Array<any>, parent?: any) {
-    (<any>arr).__owl__ = { rev: this.rev, deepRev: this.rev, parent };
+    (<any>arr).__owl__ = {
+      rev: this.rev,
+      deepRev: this.rev,
+      parent,
+      observer: this
+    };
     Object.defineProperty(arr, "__owl__", { enumerable: false });
     (<any>arr).__proto__ = Object.create(ModifiedArrayProto);
     (<any>arr).__proto__.__observer__ = this;
@@ -145,6 +179,7 @@ export class Observer {
   ) {
     var self = this;
     Object.defineProperty(obj, key, {
+      configurable: true,
       enumerable: true,
       get() {
         return value;
diff --git a/src/store.ts b/src/store.ts
index 35d1e462..853d0231 100644
--- a/src/store.ts
+++ b/src/store.ts
@@ -21,7 +21,7 @@ import { Observer } from "./observer";
 // Store Definition
 //------------------------------------------------------------------------------
 
-type Mutation = ({ state, commit, set, getters }, payload: any) => void;
+type Mutation = ({ state, commit, getters }, payload: any) => void;
 type Action = ({ commit, state, dispatch, env, getters }, payload: any) => void;
 type Getter = ({ state, getters }, payload) => any;
 
@@ -46,7 +46,6 @@ export class Store extends EventBus {
   debug: boolean;
   env: any;
   observer: Observer;
-  set: any;
   getters: { [name: string]: (payload?) => any };
 
   constructor(config: StoreConfig, options: StoreOption = {}) {
@@ -65,7 +64,6 @@ export class Store extends EventBus {
     if (this.debug) {
       this.history.push({ state: this.state });
     }
-    this.set = this.observer.set.bind(this.observer);
 
     for (let entry of Object.entries(config.getters || {})) {
       const name: string = entry[0];
@@ -110,7 +108,6 @@ export class Store extends EventBus {
       {
         commit: this.commit.bind(this),
         state: this.state,
-        set: this.set,
         getters: this.getters
       },
       payload
diff --git a/tests/observer.test.ts b/tests/observer.test.ts
index f1e15144..70b3cdbd 100644
--- a/tests/observer.test.ts
+++ b/tests/observer.test.ts
@@ -134,6 +134,57 @@ describe("observer", () => {
     expect(arr[0].__owl__.rev).toBe(3);
   });
 
+  test("set new property on observed object", async () => {
+    const observer = new Observer();
+    observer.notifyCB = jest.fn();
+    const state: any = { a: 1 };
+    observer.observe(state);
+    expect(state.__owl__.rev).toBe(1);
+    expect(observer.rev).toBe(1);
+    expect(observer.notifyCB).toBeCalledTimes(0);
+
+    Observer.set(state, "b", 8);
+    await nextMicroTick();
+    expect(state.__owl__.rev).toBe(2);
+    expect(observer.rev).toBe(2);
+    expect(observer.notifyCB).toBeCalledTimes(1);
+    expect(state.b).toBe(8);
+  });
+
+  test("delete property from observed object", async () => {
+    const observer = new Observer();
+    observer.notifyCB = jest.fn();
+    const state: any = { a: 1, b: 8 };
+    observer.observe(state);
+    expect(state.__owl__.rev).toBe(1);
+    expect(observer.rev).toBe(1);
+    expect(observer.notifyCB).toBeCalledTimes(0);
+
+    Observer.delete(state, "b");
+    await nextMicroTick();
+    expect(state.__owl__.rev).toBe(2);
+    expect(observer.rev).toBe(2);
+    expect(observer.notifyCB).toBeCalledTimes(1);
+    expect(state).toEqual({ a: 1 });
+  });
+
+  test("set element in observed array", async () => {
+    const observer = new Observer();
+    observer.notifyCB = jest.fn();
+    const state: any = ["a"];
+    observer.observe(state);
+    expect(state.__owl__.rev).toBe(1);
+    expect(observer.rev).toBe(1);
+    expect(observer.notifyCB).toBeCalledTimes(0);
+
+    Observer.set(state, 1, "b");
+    await nextMicroTick();
+    expect(state.__owl__.rev).toBe(2);
+    expect(observer.rev).toBe(2);
+    expect(observer.notifyCB).toBeCalledTimes(1);
+    expect(state).toEqual(["a", "b"]);
+  });
+
   test("properly observe arrays in object", () => {
     const observer = new Observer();
     const state: any = { arr: [] };
diff --git a/tests/store.test.ts b/tests/store.test.ts
index 2a0a81f4..88f12f82 100644
--- a/tests/store.test.ts
+++ b/tests/store.test.ts
@@ -152,24 +152,6 @@ describe("basic use", () => {
     store.dispatch("someaction");
   });
 
-  test("set function is given to mutations", async () => {
-    let updateCounter = 0;
-    const state = { bertinchamps: "brune" };
-    const mutations = {
-      addInfo({ state, set }) {
-        set(state, "chouffe", "blonde");
-      }
-    };
-    const store = new Store({ state, mutations, actions: {} });
-    store.on("update", null, () => updateCounter++);
-
-    expect(updateCounter).toBe(0);
-    store.commit("addInfo");
-    await nextMicroTick();
-    expect(updateCounter).toBe(1);
-    expect(store.state).toEqual({ bertinchamps: "brune", chouffe: "blonde" });
-  });
-
   test("can have getters from store", async () => {
     const state = {
       beers: {