diff --git a/README.md b/README.md
index 5fb5378..2ae1a61 100644
--- a/README.md
+++ b/README.md
@@ -67,6 +67,10 @@ Options include:
 }
 ```
 
+#### `mux = Protomux.from(stream | muxer, [options])`
+
+Helper to accept either an existing muxer instance or a stream (which creates a new one).
+
 #### `const p = mux.addProtocol(opts)`
 
 Add a new protocol.
diff --git a/index.js b/index.js
index abc739c..8741416 100644
--- a/index.js
+++ b/index.js
@@ -107,6 +107,7 @@ module.exports = class Protomux {
     this.corked = 0
     this.backlog = backlog
     this.onacceptprotocol = onacceptprotocol || (() => this._unopened < this.backlog)
+    this.isProtomux = true
 
     this._unopened = 0
     this._batch = null
@@ -117,6 +118,10 @@ module.exports = class Protomux {
     this.stream.on('close', this._shutdown.bind(this))
   }
 
+  static from (other, opts) {
+    return other.isProtomux === true ? other : new Protomux(other, opts)
+  }
+
   sendKeepAlive () {
     this.stream.write(this._alloc(0))
   }