diff --git a/README.md b/README.md
index 9221ae7..62fda39 100644
--- a/README.md
+++ b/README.md
@@ -50,21 +50,26 @@ const customer = form.mutators.pop('customers')
 
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
 
-* [Mutators](#mutators)
-  * [`form.mutators.insert(name: string, index:number, value: any) => undefined`](#formmutatorsinsertname-string-indexnumber-value-any--undefined)
-  * [`form.mutators.move(name: string, from: number, to: number) => undefined`](#formmutatorsmovename-string-from-number-to-number--undefined)
-  * [`form.mutators.pop(name: string) => any`](#formmutatorspopname-string--any)
-  * [`form.mutators.push(name: string, value: any) => void`](#formmutatorspushname-string-value-any--void)
-  * [`form.mutators.remove(name: string, index: number) => any`](#formmutatorsremovename-string-index-number--any)
-  * [`form.mutators.shift(name: string) => any`](#formmutatorsshiftname-string--any)
-  * [`form.mutators.swap(name: string, indexA: number, indexB: number) => void`](#formmutatorsswapname-string-indexa-number-indexb-number--void)
-  * [`form.mutators.unshift(name: string, value: any) => void`](#formmutatorsunshiftname-string-value-any--void)
+- [🏁 Final Form Arrays](#%F0%9F%8F%81-final-form-arrays)
+  - [Installation](#installation)
+  - [Usage](#usage)
+  - [Table of Contents](#table-of-contents)
+  - [Mutators](#mutators)
+    - [`form.mutators.insert(name: string, index: number, value: any) => undefined`](#formmutatorsinsertname-string-index-number-value-any--undefined)
+    - [`form.mutators.move(name: string, from: number, to: number) => undefined`](#formmutatorsmovename-string-from-number-to-number--undefined)
+    - [`form.mutators.pop(name: string) => any`](#formmutatorspopname-string--any)
+    - [`form.mutators.push(name: string, value: any) => void`](#formmutatorspushname-string-value-any--void)
+    - [`form.mutators.remove(name: string, index: number) => any`](#formmutatorsremovename-string-index-number--any)
+    - [`form.mutators.shift(name: string) => any`](#formmutatorsshiftname-string--any)
+    - [`form.mutators.swap(name: string, indexA: number, indexB: number) => void`](#formmutatorsswapname-string-indexa-number-indexb-number--void)
+    - [`form.mutators.update(name: string, index: number, value: any) => void`](#formmutatorsupdatename-string-index-number-value-any--void)
+    - [`form.mutators.unshift(name: string, value: any) => void`](#formmutatorsunshiftname-string-value-any--void)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 
 ## Mutators
 
-### `form.mutators.insert(name: string, index:number, value: any) => undefined`
+### `form.mutators.insert(name: string, index: number, value: any) => undefined`
 
 Inserts a value into the specified index of the array field.
 
@@ -93,6 +98,10 @@ Removes a value from the beginning of the array field. Returns the value.
 
 Swaps the position of two values in the array field.
 
+### `form.mutators.update(name: string, index: number, value: any) => void`
+
+Updates a value of the specified index of the array field.
+
 ### `form.mutators.unshift(name: string, value: any) => void`
 
 Inserts a value onto the beginning of the array field.
diff --git a/src/index.d.test.ts b/src/index.d.test.ts
index cf0610d..1b7d4a2 100644
--- a/src/index.d.test.ts
+++ b/src/index.d.test.ts
@@ -21,4 +21,5 @@ mutators.push('customers', { firstName: '', lastName: '' })
 const removed = mutators.remove('customers', 0)
 const shifted = mutators.shift('customers')
 mutators.swap('customers', 0, 1)
+mutators.update('customers', 0, { firstName: '', lastName: '' })
 mutators.unshift('customers', { firstName: '', lastName: '' })
diff --git a/src/index.d.ts b/src/index.d.ts
index b80b48b..b3e9f3d 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -7,6 +7,7 @@ export const push: Mutator
 export const remove: Mutator
 export const shift: Mutator
 export const swap: Mutator
+export const update: Mutator
 export const unshift: Mutator
 
 export interface DefaultType {
@@ -17,6 +18,7 @@ export interface DefaultType {
   remove: Mutator
   shift: Mutator
   swap: Mutator
+  update: Mutator
   unshift: Mutator
 }
 
@@ -32,5 +34,6 @@ export interface Mutators {
   remove: (name: string, index: number) => any
   shift: (name: string) => any
   swap: (name: string, indexA: number, indexB: number) => void
+  update: (name: string, index: number, value: any) => void
   unshift: (name: string, value: any) => void
 }
diff --git a/src/index.js b/src/index.js
index d170667..26fadaf 100644
--- a/src/index.js
+++ b/src/index.js
@@ -8,6 +8,7 @@ import remove from './remove'
 import shift from './shift'
 import swap from './swap'
 import unshift from './unshift'
+import update from './update'
 
 const mutators: { [string]: Mutator } = {
   insert,
@@ -17,6 +18,7 @@ const mutators: { [string]: Mutator } = {
   remove,
   shift,
   swap,
-  unshift
+  unshift,
+  update
 }
 export default mutators
diff --git a/src/index.js.flow b/src/index.js.flow
index 23cc240..08cec50 100644
--- a/src/index.js.flow
+++ b/src/index.js.flow
@@ -14,5 +14,6 @@ export type Mutators = {
   remove: (name: string, index: number) => any,
   shift: (name: string) => any,
   swap: (name: string, indexA: number, indexB: number) => void,
+  update: (name: string, index: number, value: any) => void,
   unshift: (name: string, value: any) => void
 }
diff --git a/src/update.js b/src/update.js
new file mode 100644
index 0000000..cc2168f
--- /dev/null
+++ b/src/update.js
@@ -0,0 +1,22 @@
+// @flow
+import type { MutableState, Mutator, Tools } from 'final-form'
+
+type Args = [string, number, any]
+
+const update: Mutator = (
+  [name, index, value]: Args,
+  state: MutableState,
+  { changeValue }: Tools
+) => {
+  changeValue(
+    state,
+    name,
+    (array: ?(any[])): any[] => {
+      const copy = [...(array || [])]
+      copy.splice(index, 1, value)
+      return copy
+    }
+  )
+}
+
+export default update
diff --git a/src/update.test.js b/src/update.test.js
new file mode 100644
index 0000000..0084e1b
--- /dev/null
+++ b/src/update.test.js
@@ -0,0 +1,38 @@
+import update from './update'
+
+describe('update', () => {
+  const getOp = (index, value) => {
+    const changeValue = jest.fn()
+    update(['foo', index, value], {}, { changeValue })
+    return changeValue.mock.calls[0][2]
+  }
+
+  it('should call changeValue once', () => {
+    const changeValue = jest.fn()
+    const state = {}
+    const result = update(['foo', 0, 'bar'], state, { changeValue })
+    expect(result).toBeUndefined()
+    expect(changeValue).toHaveBeenCalled()
+    expect(changeValue).toHaveBeenCalledTimes(1)
+    expect(changeValue.mock.calls[0][0]).toBe(state)
+    expect(changeValue.mock.calls[0][1]).toBe('foo')
+    expect(typeof changeValue.mock.calls[0][2]).toBe('function')
+  })
+
+  it('should treat undefined like an empty array', () => {
+    const op = getOp(0, 'bar')
+    const result = op(undefined)
+    expect(Array.isArray(result)).toBe(true)
+    expect(result.length).toBe(1)
+    expect(result[0]).toBe('bar')
+  })
+
+  it('should update value of the specified index', () => {
+    const op = getOp(1, 'd')
+    const array = ['a', 'b', 'c']
+    const result = op(array)
+    expect(result).not.toBe(array) // copied
+    expect(Array.isArray(result)).toBe(true)
+    expect(result).toEqual(['a', 'd', 'c'])
+  })
+})