diff --git a/docs/api.md b/docs/api.md
index 3efe63782..15570949a 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -30,6 +30,12 @@
   * [pino.stdTimeFunctions](#pino-stdtimefunctions)
   * [pino.symbols](#pino-symbols)
   * [pino.version](#pino-version)
+* [Interfaces](#interfaces)
+  * [MultiStreamRes](#multistreamres)
+  * [StreamEntry](#streamentry)
+  * [DestinationStream](#destinationstream)
+* [Types](#types)
+  * [Level](#level-1)
 
 <a id="export"></a>
 ## `pino([options], [destination]) => logger`
@@ -1164,9 +1170,10 @@ finalLogger.info('exiting...')
 
 <a id="pino-multistream"></a>
 
-### `pino.multistream(options) => Stream`
+### `pino.multistream(streamsArray, opts) => MultiStreamRes`
 
-Create a stream composed by multiple destination streams:
+Create a stream composed by multiple destination streams and returns an
+object implementing the [MultiStreamRes](#multistreamres) interface.
 
 ```js
 var fs = require('fs')
@@ -1272,3 +1279,56 @@ for general use.
 Exposes the Pino package version. Also available on the logger instance.
 
 * See [`logger.version`](#version)
+
+## Interfaces
+<a id="pino-multistreamres"></a>
+
+### `MultiStreamRes`
+  Properties:
+
+  * `write(data)`
+    - `data` Object | string
+    - Returns: void
+
+ Write `data` onto the streams held by the current instance.
+ *  `add(dest)`
+    - `dest` [StreamEntry](#streamentry) | [DestinationStream](#destinationstream)
+    - Returns: [MultiStreamRes](#multistreamres)
+
+ Add `dest` stream to the array of streams of the current instance.
+ * `flushSync()`
+   - Returns: `undefined`
+
+ Call `flushSync` on each stream held by the current instance.
+ * `minLevel`
+   - number
+
+ The minimum level amongst all the streams held by the current instance.
+ * `streams`
+    - Returns: [StreamEntry[]](#streamentry)
+
+ The array of streams currently held by the current instance.
+ * `clone(level)`
+    - `level` [Level](#level-1)
+    - Returns: [MultiStreamRes](#multistreamres)
+
+ Returns a cloned object of the current instance but with the the provided `level`.
+
+### `StreamEntry`
+  Properties:
+
+  * `stream`
+    - DestinationStream
+  * `level`
+    - Optional: [Level](#level-1)
+
+### `DestinationStream`
+  Properties:
+
+  * `write(msg)`
+    - `msg` string
+
+## Types
+### `Level`
+
+  * Values: `"fatal"` | `"error"` | `"warn"` | `"info"` | `"debug"` | `"trace"`
diff --git a/lib/multistream.js b/lib/multistream.js
index 96527986b..45213edd2 100644
--- a/lib/multistream.js
+++ b/lib/multistream.js
@@ -6,9 +6,10 @@ const { levels } = require('./levels')
 const defaultLevels = Object.create(levels)
 defaultLevels.silent = Infinity
 
+const DEFAULT_INFO_LEVEL = levels.info
+
 function multistream (streamsArray, opts) {
   let counter = 0
-
   streamsArray = streamsArray || []
   opts = opts || { dedupe: false }
 
@@ -77,22 +78,39 @@ function multistream (streamsArray, opts) {
   }
 
   function add (dest) {
+    if (!dest) {
+      return res
+    }
+
+    // Check that dest implements either StreamEntry or DestinationStream
+    const isStream = typeof dest.write === 'function' || dest.stream
+    const stream_ = dest.write ? dest : dest.stream
+    // This is necessary to provide a meaningful error message, otherwise it throws somewhere inside write()
+    if (!isStream) {
+      throw Error('stream object needs to implement either StreamEntry or DestinationStream interface')
+    }
+
     const { streams } = this
-    if (typeof dest.write === 'function') {
-      return add.call(this, { stream: dest })
-    } else if (typeof dest.levelVal === 'number') {
-      return add.call(this, Object.assign({}, dest, { level: dest.levelVal, levelVal: undefined }))
+
+    let level
+    if (typeof dest.levelVal === 'number') {
+      level = dest.levelVal
     } else if (typeof dest.level === 'string') {
-      return add.call(this, Object.assign({}, dest, { level: levels[dest.level] }))
-    } else if (typeof dest.level !== 'number') {
-      // we default level to 'info'
-      dest = Object.assign({}, dest, { level: 30 })
+      level = levels[dest.level]
+    } else if (typeof dest.level === 'number') {
+      level = dest.level
     } else {
-      dest = Object.assign({}, dest)
+      level = DEFAULT_INFO_LEVEL
+    }
+
+    const dest_ = {
+      stream: stream_,
+      level,
+      levelVal: undefined,
+      id: counter++
     }
-    dest.id = counter++
 
-    streams.unshift(dest)
+    streams.unshift(dest_)
     streams.sort(compareByLevel)
 
     this.minLevel = streams[0].level
diff --git a/pino.d.ts b/pino.d.ts
index 31efc4f7b..b1be3867f 100644
--- a/pino.d.ts
+++ b/pino.d.ts
@@ -261,10 +261,10 @@ declare namespace pino {
 
     interface MultiStreamRes {
         write: (data: any) => void,
-        add: (dest: Record<string, any>) => MultiStreamRes,
+        add: (dest: StreamEntry | DestinationStream) => MultiStreamRes,
         flushSync: () => void,
         minLevel: number,
-        streams: ({ stream: DestinationStream, level: number, id: number })[],
+        streams: StreamEntry[],
         clone(level: Level): MultiStreamRes,
     }
 
diff --git a/test/multistream.test.js b/test/multistream.test.js
index 94ae848bf..7073148a2 100644
--- a/test/multistream.test.js
+++ b/test/multistream.test.js
@@ -481,7 +481,7 @@ test('no stream', function (t) {
   t.end()
 })
 
-test('add a stream', function (t) {
+test('one stream', function (t) {
   let messageCount = 0
   const stream = writeStream(function (data, enc, cb) {
     messageCount += 1
@@ -497,6 +497,43 @@ test('add a stream', function (t) {
   t.end()
 })
 
+test('add a stream', function (t) {
+  let messageCount = 0
+  const stream = writeStream(function (data, enc, cb) {
+    messageCount += 1
+    cb()
+  })
+
+  const log = pino({
+    level: 'trace'
+  }, multistream().add(stream))
+  log.info('info stream')
+  log.debug('debug stream')
+  log.fatal('fatal stream')
+  t.equal(messageCount, 2)
+  t.end()
+})
+
+test('multistream.add throws if not a stream', function (t) {
+  try {
+    pino({
+      level: 'trace'
+    }, multistream().add({}))
+  } catch (_) {
+    t.end()
+  }
+})
+
+test('multistream throws if not a stream', function (t) {
+  try {
+    pino({
+      level: 'trace'
+    }, multistream({}))
+  } catch (_) {
+    t.end()
+  }
+})
+
 test('flushSync', function (t) {
   const tmp = join(
     os.tmpdir(),
diff --git a/test/types/pino-multistream.test-d.ts b/test/types/pino-multistream.test-d.ts
index cc2f6863c..6006f9c53 100644
--- a/test/types/pino-multistream.test-d.ts
+++ b/test/types/pino-multistream.test-d.ts
@@ -21,5 +21,6 @@ expectType<pino.MultiStreamRes>(pino.multistream(streams))
 expectType<pino.MultiStreamRes>(pino.multistream(streams, {}))
 expectType<pino.MultiStreamRes>(pino.multistream(streams, { levels: { 'info': 30 } }))
 expectType<pino.MultiStreamRes>(pino.multistream(streams, { dedupe: true }))
+expectType<pino.MultiStreamRes>(pino.multistream(streams[0]).add(streams[1]))
 
 expectType<pino.MultiStreamRes>(multistream(process.stdout));